Abstract: Based on the IEEE802.15.3a proposal and ECMA-368 standard, the multi-band orthogonal frequency division multiplexing ultra wideband (MB-OFDM-UWB) baseband system was established including channel coding and decoding, interleaver and deinterleaver, digital modulation and demodulation, frame structure constitution, frequency hopping and dehopping. A technique of digital baseband frequency hopping and dehopping was proposed to realize multi-band modulation for this system. Synchronization technologies for the system were also researched. First the system designed was built in the Matlab simulation platform and verified feasible. On this basis, using FPGA development board, the hardware system was implemented. Testing the performance of this system is the final step. The simulation results indicate that the system designed has a good performance of transmit and receive data. It's also a hardware experimental platform for the research on other key technologies.