The embodiment of the invention provides a lightweight RFID mutual authentication method based on time factors against desynchronization. The method comprises the following steps: mutual verification between a label and a reader-writer is realized in a way that a back-end database and the label share old and new secret keys, randomized numbers and time factors are adopted as fresh quantities and encryption calculating is conducted, the randomized numbers are generated by the back-end database each time, the time factors are stored and updated by the label, and Hash operation and cyclic shift calculation are conducted during each verification process between the back-end database and the label according to stored secret key information. The method has good security and privacy protection performance, can well resist desynchronization attacks from attackers, can protect content privacy, position privacy and forward and backward security, and can resist playback attacks, eavesdropping and other attacks.