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, an investigation about the encoding and modulation technologies of the UAT2 data link transmitter was conducted. The system structure of the UAT2 data link transmitter was 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 was developed, which significantly reduced execution time and memory usage. CPFSK modulation was implemented based on direct digital synthesizer (DDS) technology. The signal requirements of the UAT2 data link were met and the spectral energy distribution was ensured to be concentrated. The encoding and modulation key technologies were tested and evaluated for performance. The results verified their effectiveness and applicability to the UAT2 data link transmitter.