Aiming at the problem of poor bit error performance of space pulse position modulation(SPPM) in vertical link, concatenated channel coding is used to improve the bit error performance of the system. The bit error performance of low density parity check(LDPC) code and polar code under different code length and different code rate is compared and analyzed. The simulation results show that when the bit error rate is 10-4 and the bit rate is 0.5, polar code has a better performance than LDPC code about 2 dB. When the bit rate is 0.8, the bit error performance of the two systems is almost the same, and the performance gap is gradually narrowed when the bit rate increases. In SPPM system, concatenated channel coding can effectively improve the system error performance.