Disclosed are a signal processing method, a base station, a terminal, and a system. A base station side method comprises: sending a synchronization signal to a terminal through a predetermined first time-frequency resource; sending a supplemental synchronization signal different from the synchronization signal to the terminal through a predetermined second time-frequency resource, the synchronization signal and the supplemental synchronization signal being corresponding to a same physical layer cell identifier. In the technical solution provided by the embodiments of the present invention, in addition to that the synchronization signal is sent, the supplemental synchronization signal is also sent, and it is equivalent to increase of the transmission frequency of the synchronization signal. In a case where the network coverage is poor, the increase of the transmission frequency of the synchronization signal can increase the probability that the terminal completes cell searching by performing relevant detection on the same number of signals, so as to not only shorten the time required by the terminal to perform cell searching, but also decrease the amount of data buffered by the terminal, thereby decreasing the requirements on the buffer of the terminal.