IMS session processing method and system

The present invention relates to a processing method of the IMS conversation, which comprises that step 11, whether the registered information of a called party exists is estimated by a calling side S-CSCF, if the registered information of a called party exists, step 12 is executed, otherwise, the S-CSCF analyzes the destination address according to the called party PUI, to retransmit the Invite request to the relevant I-CSCF, and the I-CSCF processes the Invite request according to the 3GPP standard conversation flow; step 12, the S-CSCF checks the state of the called party PUI and the signed contract information, and processes the called party PUI and the signed contract information. The present invention expands the S-CSCF function in a certain grade on the basis of the 3GPP IMS conversation flow, optimizes the IMS conversation processing flow, to reduce the unnecessary signaling interaction during the IMS intraoffice conversation, effectively decreases the signaling flow and the processing load of the equipment, and advances the service quality.