The invention discloses a radio frequency identification (RFID) safety communication method established according to an ultra-lightweight RFID bidirectional authentication protocol. By adoption of the method, the security problems of a low-grade tag RFID system can be effectively solved. The method has the main characteristics of security, high efficiency, simplicity and practicability. A tag is only required to provide simple operation such as random number generator operation, exclusive-OR operation, modular operation (MOD) and displacement. Resources required by the simple operation are extremely limited, so the scheme is in complete accordance with an EPCglobal C1G2 tag specification, has the characteristics of low storage cost, low operation cost, low communication cost, novel and simple algorithm and the like, and is easy to implement. The method has the advantages that the problems about synchronization of the tag and a rear-end database key, forward security and security privacy (privacy leak, flow analysis and positioning tracking) can be effectively solved, and the common security problems of an RFID system about imitation attack, cloning attack, monitoring attack, replay attack and denial-of-service attack are solved. The method is quite applicable to solving the security problems of an EPCglobal C1G2 RFID tag.