The data link capacity of 1090ES (1090 MHz Extended Squitter) could be expended by modulating 1090 MHz signal with phase information, thus RS (Reed-Solomon) calibration technology of 1090ES expansion system based on 8PSK (8 Phase Shift Keying) phase modulation was studied. Firstly, the total length of the RS code symbols was designed as 54 according to the characteristics of RS code and the data link structure of 1090ES expansion system. Secondly, error performance with different RS code coding efficiency was discussed, and its influence on performance of the 1090ES expansion system was analyzed, thereby, the optimum selection of RS code coding efficiency range was determined as 0.6-0.7. Finally, the concrete analysis of the error performance in the selected encoding efficiency range was given, and then the experimental results show that the length of information symbols could be chosen as 32, 34 or 36. Furthermore, Matlab simulation analysis shows that the designed RS code can effectively improve the error performance of 1090ES expansion system with RS(54, 32) as an example.