With the development of communication technology and the highly valued position of space area, space optical communication technology has become one of the hot spots in the world. At present, the ground optical communication is developing very fast, and a variety of difficulties has already been broken through for amplification techniques, especially those based on fiber amplifier have been widely used, and the technology is very mature. As the fiber-type devices are very sensitive to the radiation environment of the space, if the external modulation technology which has been successfully used in ground optical communications is used in space environment, we must consider the feasibility of the erbium doped fiber amplifier (EDFA) which is the core device in the external modulation technology and analyze the corresponding anti-radiation technique. This paper analyzes the space radiation environment and its effect on the performance of EDFA. Approaches including fading center anti-radiation technique, pre-radiation and hydrogen loading active anti-radiation technique and fiber manufacturing technology of anti-radiation technique are proposed to improve the space radiation resistant performance of the EDFA systems. A theoretical basis is provided for the application of EDFA in space optical communications. Through the experimental study, it is found that by adopting the above anti-radiation methods, the radiative decay of 1550 nm erbium-doped fiber (EDF) can be reduced by 0.8 dB/km theoretically.