Method for preventing replay attack and server

The invention provides a method for preventing a replay attack and server. The method includes the following steps: a server receives a service request message, a timestamp is analyzed from a unique identifier of the message, and whether the timestamp is in a preset time window of the server is determined, if the timestamp is in the time window, the unique identifier of the message is further compared with identifiers in a stored received message identifier list, if an identifier which is the same as the unique identifier of the message is not contained in the list, the service request message is not considered as a replay attack, and service processing can be performed. The method provided by the invention further improves network security.