The invention relates to the technical field of two-way digital television condition accepting systems and network communication, in particular to a method for realizing communication between a two-way CAS gateway and a user terminal based on an IOCP. The invention discloses the method for realizing the communication between the two-way CAS gateway and the user terminal based on the IOCP, which solves the problem that a communication mode in the prior art can hardly meet actual operational requirements. The method adopts the main points of the technical scheme of: monitoring a set-top box terminal; if a user issues a connection, establishing an IOCP work thread, accepting the connection and associating a socket with an IOCP target; and after receiving request information transmitted by the user terminal, resolving the request information, transmitting the resolved request information to a CAS front end and forwarding the returned information of the CAS front end to the user terminal. The method has the advantages of increasing the parallel access number of the user terminals, improving the running efficiency of the two-way CAS and being applied to the communication between the two-way CAS gateway and the user terminal.