Abstract: In order to satisfy the miniaturization, high accuracy and high reliability of spaceborne reflection photoelectric encoder, the signal processing system was designed. Firstly, the overall design of the signal process system spaceborne reflection photoelectric encoder was represented. Then, methods of processing precise code and coarse code were given, and the data processing system was integrated into main system which used FPGA, the size was decreased, at the same time the electric circuit was cold backup to improve the reliability. Finally, 23 surfaces polyhedron and autocollimation were used to test the accuracy. The experiment results show that the resolution is 0.3(22 bit), the primary precision was =2.22(3=6.65), the standby precision is =2.69(3=8.07), by using this signal processing system. By applying to practical projects, the processing system had satisfied the technique reqirement of the spaceborne equipment.