A background service process unit for a browser based call center position system, characterized by , comprising a protocol stack module , a state machine module , a service end access interface module and a real-time protocol, RTP, protocol stack module , wherein the protocol stack module , connected to a computer telephony integration, CTI, server and an automatic call distributor, ACD, is configured to send and receive a telephony service application programming interface, TSAPI, message and a session initiation protocol, SIP, message, analyze a result of message sending and content of a received message, and deliver an analyzed message to the state machine module for processing; the state machine module , interfaced with the service end access interface module , is configured to provide validity detection for an operation of a customer representative according to a position state and/or a call state, and maintain the position state and the call state according to the TSAPI message and the SIP message that have been received; the service end access interface module is configured to provide interfaces of position state and call state control for the customer representative; wherein the protocol stack module comprises a TSAPI protocol stack module and a SIP protocol stack module , and the state machine module comprises a position state machine module and a call state machine module , the TSAPI protocol stack module is connected to the CTI server, and the SIP protocol stack module is connected to the ACD, the service end access interface module is specifically configured to receive a call operation request; the position state machine module is configured to judge whether an operation of the call operation request can be performed currently, if yes, send the call operation request to the CTI server through the TSAPI protocol stack module ; the position state machine module is also configured to, after receiving an operation initiation confirmation message sent by the CTI server, make a corresponding switching to the position state, and send a corresponding operation result to an operation page currently opened by a position through the service end access interface module ; the SIP protocol stack module is configured to, after receiving a call operation command sent by the ACD, send a corresponding media stream control instruction to the RTP protocol stack module , and simultaneously inform the call state machine module of the call operation command; the RTP protocol stack module is configured to, after receiving the media stream control instruction, perform a corresponding media stream control operation; the call state machine module is configured to, after receiving the call operation command, make a corresponding switching to the call state, thereafter return to the ACD an operation completion confirmation message through the SIP protocol stack module ; the TSAPI protocol stack module is configured to, after receiving the operation completion notification message sent by the CTI server, make a corresponding switching to the position state, and send an operation completion notification message to the operation page opened currently by the position through the service end access interface module. <EOS>