The present disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates than 4G systems such as LTE. A method for operating a proxy in a wireless communication system combining a terrestrial network and a satellite network according to an embodiment of the present invention comprises the steps of: acquiring, from a server for managing a satellite, configuration information about a satellite cell that connects with a user equipment in which a transport control protocol (TCP) session is to be set up; calculating a first round trip time (RTT) between the satellite cell and the satellite and the data rate of the satellite cell on the basis of the configuration information about the satellite cell; and setting a congestion window (CWND) value for the TCP session on the basis of the first RTT and the data rate of the satellite cell.