The invention relates to a method for enhancing communication safety in an industrial control system. The method is applied in the industrial control system. The industrial control system comprises a master station side and a terminal side which are in communication with each other. The method is implemented through a preparation stage before communication, a master station side sending stage, and a terminal side receiving, processing and replying stage. The method is used for solving the problems that in communication of an existing industrial control system, the computing capacity of a client is weak, time of the client comes from a server, a communication channel is not reliable, and instantaneity and high safety are needed for key communication. The method is designed for safety communication in the special environment, identity authentication and a complete guarantee are provided for a key communication message, and safety of the whole system is effectively enhanced.