The simulation of a time resolved electron microscope is discussed.Temporal resolution and spatial resolution power are evaluated by computing the motion of transmission eletrons emitted from the sample in the combination of static magnetic field and dynamic electric field.The design methods,including the calculation of magnetic field,dynamic electric magnetic field,electron trajectory tracing and spatial and temporal spread functions,are also involved.The simulation demonstrates that 6 framing images with the size of φ=10mm,temporal resolution of 100ps and spatial resolution of 100Å have been achieved in the time resolved electron microscope.