Abstarct: Whenever magnetic particles are placed within a magnetic field, magnetic force applies to them. To create a local magnetic gradient within the microchannel, the idea is to use ferromagnetic wires. The feature that distinguishes this system is the idea of using two ferromagnetic wires in the microchannel at the same time. With this design, we were able to separate and collect two types of magnetic particles with different sizes from each other and from the fluid flow simultaneously. This system has been studied numerically in this research. In order to numerically analyze the system, we first determine the governing equations and then solve these equations according to the system configuration, using CFD simulation software. To measure the accuracy of the simulations, the result of a particular model is compared with the result of the analytical relation extracted for the same case, which results 4% error. Also, the dependency of the simulation to the grid size is investigated and the appropriate grid size is selected. For simpler and faster modeling of the equations, it is assumed that the effect of the particles on the fluid flow field and the magnetic field is negligible. The two particle types used in this study are M-280 and M-450 particles, which are magnetic and the characteristics of each is known. After performing simulations and analyzing different cases, we determined that in order to collecting these two types particles, the diameter of the first wire is 50µm and the diameter of the second wire is 100µm, the distance between the wires is within 800µm and 900µm, the particles solution inlet located at the 200µm to 300µm from the center of the channel, the applied external magnetic field inside the channel is 0.5 Tesla (which is obtained by placing the B222G-N52 permanent magnet in 3.1mm from the center of the microchannel) and also the fluid enters the channel at an average velocity of 11mm/s. By selecting the parameters of the proposed system equal to the specified values, we were able to collect particles M-280 and M-450 with an efficiency of 97% in the microchannel, so that particles M-450 are collected around the first wire and particles M-280 are collected around the second wire. By changing some of this system parameters such as wire diameter or fluid flow velocity or magnetic field intensity, this system can be used for other applications or particles with different properties.