A transmission opportunity determining method and an access point are provided, so as to implement a transmission opportunity determining method for multiuser transmission and further improve multiuser transmission efficiency. The method includes: determining, by an access point, transmission opportunity duration in which the access point performs frame transmission with at least two stations for a plurality of times; and after the access point performs backoff and obtains a channel through contention, and initially sends a downlink frame in the transmission opportunity duration, determining, by the access point, that the access point holds a transmission opportunity in the transmission opportunity duration.