Abstract: To address the issues of insufficient data transmission reliability and low coding efficiency of the traditional Reed-Solomon (RS) coding in the Enhanced Long-Range Navigation (eLoran) system under complex electromagnetic environments. From the perspective of joint design of the transmitter and receiver systems, an enhanced Loran coding and modulation design scheme based on polar codes is proposed. This scheme replaces traditional RS coding with polar coding, obtains the soft information required for polar codes through soft demodulation, and develops a decoding method that combines polar coding with three-state pulse position modulation. Simulation results show that the proposed scheme can achieve a coding gain of about 2.3 dB at a frame error rate (FER) of 0.01, compared with the traditional scheme. This validates the feasibility and superiority of the three-state pulse position modulation system based on polar codes in eLoran systems.