Abstract: Finite-difference time-domain method and particle-in-cell simulation were combined to simulate the beam transport process in linear induction accelerators. The non-uniform grid model was used to fulfill the three-dimensional simulation modeling of the accelerator gap, and electric field was generated at the gap. The magnetic field distribution was calculated with three steps, which was generated by the solenoid mounted inside the accelerating cell. Combining the focusing magnetic field with the acceleration section, the electron beam transport process was simulated and its results were analyzed, proving the validity of this method.