Abstract: In order to improve the technical performance of relay protection products, enhance the standardization design level and meet the requirements of relay protection product in design, test and operation management, the DL/T 478—2013(General Specification of Relaying Protection and Security Automatic Equipment) has been released and implemented. In view of the revised and supplementary content of the new standard, the reason for all previous revisions and technical background are introduced in detail, and the main principle is pointed that standard improvement should follow technology development. The supplementary requirements for improving performance, safety and test rule in the new edition are analyzed, which can help relay protection designers and management personels to well- understand and accurately implement the current standard.