Abstarct: In this research, for the first time, the local/non-local two-phase elasticity theory is used to investigate the vibration of a circular graphene sheet with a structural defect located in a magnetic field. When graphene is placed in a magnetic field, the Lorentz force is applied to it, which is calculated using Maxwell's equations. Due to some shortcomings of pure Eringen's non-local theory, some researchers have used two-phase elasticity theory to study nanobeams. Some defects on a graphene nanosheet may occur due to the manufacturing process and other limitations, and many of them can be modeled as holes. A circular hole is considered as a centeric and eccenteric defect on a circular graphene sheet. Dynamic equilibrium equations have been extracted and solved using Newton's method using non-local theory. In addition, the vibration equations of a graphene nanosheet with a central hole have been obtained as a differential equation of motion using local/non-local two-phase theory, which is a sixth-order differential equation and requires six boundary conditions to solve. An analytical method has been used to obtain the frequency of symmetric modes. In this study, clamped boundary conditions are assumed on both outer and inner edges and two structural boundary conditions are derived. The first three symmetrical frequencies were obtained from the analytical solution method and verified with the results of other researches. In the next step, a circular graphene nanosheet with a defect in the form of a central hole located in the magnetic field is considered. Then, the differential equations of motion are obtained. Clamped boundary conditions are assumed on both the outer and inner edges and the Gelkerkin approach is used to solve the equations. Validation of the solution is confirmed using a comparative study between the results obtained with other related researches, and the accuracy of the presented approach is confirmed. In the results section, the effectiveness of the mixture parameter, magnetic field, non-local parameter and radius ratio on the natural frequency are investigated. The results show that increasing the mixture parameter and magnetic field increases the natural frequency.