Provided by an embodiment of the present application are a method and device for determining a contention window, the method comprising: according to feedback information sent by a terminal device, a network device determining the length of a contention window (CW) used for channel detection, the feedback information comprising feedback information corresponding to a physical downlink shared channel (PDSCH) sent by the network device on a first carrier wave; according to the length of CW, the network device performing channel detection on the first carrier wave.