A method, transmitter and modulator for signal synchronization transmission in a single frequency network transmission system are disclosed. The method includes: extracting effective data from data received; performing channel coding, mapping and modulation to the effective data extracted and saving the data modulated into storage; and retrieving the data from the storage upon receiving a pulse indication signal, performing digital-to-analog conversion and baseband-to-radio frequency conversion to the data retrieved and transmitting the data converted into air via antennae. The technical scheme enables different transmitters to transmit signals synchronously.