The present invention provides a signal transmission method and apparatus, a communications system, a terminal, and a base station, where the method includes: determining a repetition factor or an extended sequence of a channel; determining a time domain resource according to the repetition factor or a length of the extended sequence, where the time domain resource is a transmission subframe; and sending a signal by using the transmission subframe of the channel. The signal transmission method, apparatus, communications system, terminal, and base station that are provided by the present invention can solve the technical problem of poor channel coverage in a signal transmission method in the prior art.