Abstract: To address the increasing number of low-altitude aerial vehicles and meet the surveillance and tracking needs of the aviation industry for future urban air mobility (UAM) vehicles, a investigation into the encoding and modulation technologies of the UAT2 data link transmitter is conducted. The system structure of the UAT2 data link transmitter is designed. Aiming at the surveillance needs of UAM vehicles, an addressable data uplink communication encoding and a vehicle health status monitoring downlink encoding algorithm are proposed to cover the safety operation requirements of UAM. A high-speed reed-solomon (RS) encoding algorithm for UAT2 messages is developed, which significantly reduced execution time and memory usage. CPFSK modulation is implemented based on direct digital synthesizer (DDS) technology, the signal requirements of the UAT2 data link is met and the spectral energy distribution is ensured to be concentrated. The encoding and modulation key technologies are tested and evaluated for performance, confirming their effectiveness and applicability to the UAT2 data link transmitter.