Abstract: Aiming at the shortcomings of the traditional pilot method in the simulation of wire operating voltage and the initial judgment of the upstream pilot,a pilot development model is estalbished. By studying the spatial electric field changes during the initial process of the upstream pilot,an improved upstream pilot initial model based on the average field strength is obtained. Compared with the Peek criterion,it is found that the traditional pilot model exaggerates the ability of thundercloud to attract the pilot. Case analysis verifies the validity of the model which is applied to analyze the shielding characteristics of transmission lines,and lightning protection measures are proposed.