When nuclear power plants adopt digital instrumentation and control (I&C) systems, the inherent complexity and unpredictable nature of software create an unprecedented challenge for software maintenance. The difficulty often comes from lacking consistence among the vendors and the requirement of nuclear safety-related regulation. The aim of Regulatory Software Maintenance Environment (RSME) with agent-based software configuration management discipline is to provide guidelines and procedures for carrying out a variety of software maintenance activities through the establishment of a systematic approach to support the operation of nuclear power plant. This paper describes a few requirements of software maintenance environment, software maintenance model, RSME with agent-based architecture with XML technology and a prototype application of the digital I&C of nuclear power plant.