Disclosed is a secure communication method of an IMS system based on a key file. The method includes obtaining an IMS account before sending the account and authentication information to a background server by a UE; generating an electronic work order by the background sever according to the received authentication information to enable customer service personnel to manually audit the authentication information and the IMS account according to a preset rule and the electronic work order; generating an encrypted key file and sending the file to the UE when determining the correctness of the authentication information and the IMS account; and activating the IMS account according to the key file and performing network communication according to the IMS account. The disclosure improves the communication security of the IMS system by using the activated IMS account for network communication.