The disclosure provides a method and a system for indicating a valid time of a trigger message, to indicate the valid time of the trigger message through a validity period parameter in the trigger message. The validity period parameter includes: a validity period format and a validity period. The method further comprises: a server transmits the trigger message to a network side entity (201); and the network side entity transmits the trigger message to a terminal after successfully parsing and storing the trigger message (202). Through the method and the system, a network is capable of correctly parsing the trigger message and implementing the valid time in the trigger message and thus avoids a wrong removal of a trigger message.