The invention relates to a multicarrier digital satellite broadcasting system and the digital information transmitting method thereof, comprising signal source coder, code modulator, transmitter, satellite, user demodulator and signal source decoder, where the signal source coder encodes analog signal into digital signal, which is transmitted to the code modulator for error control coding, constellation mapping, scrambling, OFDM modulation and signal mark addition to obtain transmitted frame group; the transmitted frame group is processed by time gap multiplexing, low-pass filtering, carrier high frequency modulation and synthesizing of various frequency data and finally transmitted to the transmitter; the transmitter transmits the high frequency signal to the satellite and is received by the user demodulator by satellite broadcast; the user demodulator detects signal and demodulates the signal into data stream and transmits the data stream to the signal source decoder to be decoded into analog signal to be outputted to terminals. And it implements flexible multiplexing of multicast services and improves system flexibility.