This paper designed an OFDM baseband signal transmission system, which adopted CORDIC algorithm, pipeline organization and high-speed floating-point butterfly unit to complete the customized FFT Processor, and the modulation of the signal was realized by enhancing modulation mode (64-QAM) in the adaptive modulation mode. Meanwhile, due to FPGA technology is reconfigurable and parallel, the signal has a higher transmission rate. The system used FPGA resources reasonably and integrated highly, simplifying the complexity of the system; eventually it was adapted to the EP2C35F672C6 chip of Altera, and can be normally operated in the clock frequency of 100 MHz; At the same time, this system the system has high flexibility and generality, simple structure, and good clutter suppression, so it has a certain application prospects.