A method for scheduling transmission in a wireless communications system, and a device are disclosed, to resolve a technical problem that uplink transmission in a cell in which the uplink transmission is performed may be interfered with by downlink transmission. The method includes: determining, by a network device, a priority of each transmission time interval used for first-direction transmission in a transmission time interval set, where the first-direction transmission is along a downlink direction from the network device to user equipment or along an uplink direction from the user equipment to the network device; selecting, by the network device, for a first cell, at least one transmission time interval from the transmission time interval set based on the priority; and performing, by the network device, in the first cell, the first-direction transmission with the user equipment by using the selected at least one transmission time interval.