The present invention discloses a digital signal receiving/sending method, which includes procedures below: During digital signal emission, data flows composed of multilevel symbols are divided into continuous data frames for emission. Preset information is added into each data frame for system synchronization, clock resetting, channel estimation and equalizer training. System information is added into each data frame to indicate modulation mode, intersection mode and LDPC coding rate of a current frame of data information. Data information is added into each data frame. Wherein, the preset information, the system information and data information form a simplex one-step circulation. While receiving digital signals, position of the preset information is detected and confirmed. A first symbol clock position next to the preset information is taken as a start of the system information. Position of the system information is detected and confirmed. A first symbol clock position next to the system information is taken as a start of the data information. Besides, signal processing is carried out to the data information. The present invention also discloses a digital signal receiving/sending system.