Abstract: The dielectric parameters of the oil-paper insulation of converter transformer are in dynamic changes under the influence of temperature and field strength during operation. However, traditional engineering design usually ignores the influence of high temperature and high field strength, and uses material parameters obtained under normal temperature and low electric field for electric field calculation. This paper established the valve side winding model of the converter transformer, and used the measured data of the oil-paper insulation dielectric parameters under different temperatures and field strengths for simulation calculations. The influences of the parameters under normal temperature and low field strength with the dynamic parameters under actual operating temperature and field strength on the electric field distribution were compared and studied. The research results show that using the fixed-value parameters to calculate the electric field has a larger design margin than the actual situation.