For the purpose of improving the reliability of the network communication in the digital instrumentation and control system of nuclear power plant,a safety communication protocol design based on DeviceNet was proposed.According to the eight kinds of commu-nication failures defined in the national standard IEC61784, we extended several safety measures to prevent those communication failures and ensure the reliability and safety of the whole communication system.In order to verify their validity,we developed a protocol stack on the MICON platform and designed some test cases.The test results sho...