Abstract: The image converter tube is a core component in the streak cameras. Its operation was introduced and the model for its internal electronic optical system was built. Numerical simulations were done by ANSYS based on the finite element method, in which the functional is solved by Hamilton principle. The distribution of the electrostatic field was calculated in an operation voltage and the tracks of electrons were calculated in different operation voltages. The results agree well with that of the symmetric electrostatic field theoretical analysis. They also indicate that the size and shape of electrode has a slight influence on imaging, and the proper voltages(containing accelerating, focusing and anode voltages) has more.