The invention discloses a baseband signal processing circuit which comprises a level adjusting circuit used for converting input signals into first level signals, a filter circuit used for filtering the first level signals and outputting filtered signals, and a differential circuit used for converting the filtered signals into differential signals. On one hand, the converted signals can be input into a modulation chip directly, so that a DAC chip is eliminated, the cost is lowered, and power consumption is reduced; and on the other hand, as the baseband signal processing circuit provided by the invention can filter signals directly, the complexity caused by arranging of a software filter in an FPGA is lowered, and the logical resource of the FPGA is saved.