The reasons of shielding failure in transmission line were investigated, as well as the method of lightning shielding failure prevention. Based on operation experiences of transmission line in Jiangxi Province, the reason of shielding failure trip of JG and ZGUT type tower were emphatically analyzed, and a new measure was proposed to prevent shielding failure trip. The results show that TH-lightning rod installed on the cross arm at wire suspension point of JG and ZGUT type tower can reduce the shielding angle of mid-phrase jumper-line of JG type tower and that of mid-phase conductor of ZGUT type tower, which can greatly decrease the lightning failure trip rate.