The transient electric field distribution of GIS basin insulator under lightning impulse voltage is of great importance for its safe operation. The establishment time of turning-direction polarization of basin insulator material under lightning impulse voltage is generally neglected

and then the electrostatic field under power frequency voltage has usually been used to replace the transient electric field in engineering. In this paper

the transient electric field calculation of the basin insulator is realized by using the established mathematical model of the transient electric field of the basin insulator and the dielectric spectrum analysis method based on LM algorithm. The distribution of transient electric field on the surface of shielding cover

basin insulator and the interface between basin and central conductor has been obtained and then investigated. The results from the traditional method have also been compared. The maximum electric field intensity on the surface of the concave shielding cover and basin is higher than that from the transient analysis. The differences are-2.2%

-1.21% and-4.37%

respectively. The difference of maximum electric field strength between two methods on the interface is about 4.46%. The method can be adopted to accurately compute the electric field distribution of each kf GIS basin insulator within an acceptable computation time. And the research in this paper can provide calculation of key position and analysis references for the insulation design of GIS basin insulator.