The present disclosure relates to the mobile communications field, and in particular, to a transmission resource determining technology in a wireless communications system. In a data transmission method, a network device determines a transmission resource used for data transmission, and performs data transmission with a terminal device on the determined transmission resource. A time domain resource occupied by the transmission resource in a time domain is one of N types of time domain resources, and a time length of any type of time domain resource in the N types of time domain resources is less than 1 ms. According to this method, a data transmission latency can be effectively reduced, thereby meeting a requirement for a low-latency service.