In view of the characteristics of space charge positions in an organic insulation dielectric under high electrical field, a surface potential model was put forward to investigate the dynamics of charge carrier capture. By the suggested comparative experimental method, trap creation under high field was expressed in the increment of surface potential. It is shown that the structural degradation is proportional to the time of the field application and to the exponential of the inverse of the field. Such a result was also verified by photoconductive current research. Taking a certain extent of trap creation as the critical condition of electrical breakdown, a widely used empirical formula about electrical aging was finally deduced.