Electrified Railway has been most potential traffic manners for its excellent dynamic and economic benefit.But it affects power system badly.This paper analyzes impact of traction substation on relay protection by combining with facts of Zhejiang-Jiangxi electrified railway and Jiangxi power system,and shows a plan of reply protection based on PSL 607 and CSC 109A digital protection system.It has been used well in Traction Substation.