Abstarct: Due to the increasing human need for energy and fossil fuels in the near future and insufficient production of renewable energies, it is believed that in the near future, energy production will require new methods. Therefore, extensive studies have been conducted to obtain energy sources. The main focus is on nuclear energy. Nuclear energy is produced in two ways; Nuclear fission and nuclear fusion. One of the advantages of nuclear fusion is cleanliness, absence of hazardous waste, safety, shutdown of the reactor in any condition, cheapness and abundance of deuterium, the primary fuel of fusion reactors, which is abundantly found in ocean water. One of the advantages of nuclear fission is the abundant energy that is created from a heavy nucleus. In fact, nuclear fusion technology contains strong neutron flux and nuclear fission technology produces high energy. Therefore, these properties are used to design fusion-fission hybrid reactors at the international level. In this thesis, one and two blanket fusion-fission hybrid reactor is designed baxsed on neutron and safety parameters. In the first chapter, the dense plasma focus and its design parameters are studied for use in hybrid reactor structure. Also, the main parameters of the device, such as electric potential and electric field of the dense plasma focus, are analyzed and simulated by COMSOL code. One of the advantages of the dense plasma focus is that with its proper design, the fusion neutron flux can be increased, its construction cost is very low, and its design is easier than other nuclear fusion devices. The device has a small volume, and it is portable, especially if it is made in the low energy range, for example below 200 kj. Considering what the reactor's performance is as a result of the interaction of neutrons with fuel and other materials inside, in the second chapter, the analysis of reactions between neutrons and nuclei is done to check the equations of neutron emission at different energies. In the third chapter, the materials used in different parts of the reactor as fuel, moderator , coolant, reflector, multiplier, fuel cladding and end cell of the reactor are briefly examined. Also, the use of nano materials in the parts of the reactor that are used is analyzed. In the fourth chapter, the first blanket design, above the fusion source, is selected due to the highest incoming neutron flux, the lowest neutron escape from the surface (geometric buckling), more suitable neutron parameters and smaller blanket volume. Then the most suitable diameter and pitch of the fuel rods in 3.77% enriched uranium in light water is determined by the MCNPX code using the Monte Carlo method, and to optimize fuel consumption, the light water cell in the center of the fuel rod for conversion fast neutrons are converted into thermal neutrons to increase the effective multiplication factor and reactor efficiency by reducing the temperature and fuel consumption. Then, the bottom wall of the blanket was designed with the proper materials and in the proper thickness so that it is resistant to particles hitting the wall and creating depressions or corrosion as much as possible and does not react with fusion neutrons. After the wall separating the blanket from the fusion cell, a neutron multiplier cell is used. Then the first blanket includes fuel rods and light water. Above the first blanket, a material is used that has the role of a reflector for the first blanket and a multiplier for the second blanket so that as little fuel as possible is used while maintaining the desired effective multiplication factor in the first blanket. To increase fission energy production in subcritical conditions, the second blanket is used. To optimize the fuel in the desired effective multiplication factor, the geometry of the second blanket is chosen in such a way that the most neutrons enter the second blanket from the first blanket. In order to maintain the safety of the first blanket, the geometry of the second blanket and its distance from the first blanket should be such that the least neutron returns from the second blanket to the first blanket. This geometry and the distance between two blankets were checked by theoretical calculations and simulated by MCNPX code. The internal structure of the second blanket, including fuel rods and light water, was considered the same as the first blanket. After the second blanket, to optimize fuel and reduce environmental pollution, a neutron reflector cell is placed and then a lithium cell is used. To produce tritium, which is used in the dense plasma focus. Finally, the concrete laxyer is simulated by the MCNPX code to prevent photons and neutrons from leaving the reactor, so that the neutrons and photons leave the reactor to zero. Then, some solutions to increase reactor efficiency are examined.