Abstract: In the space station construction, for large-tonnage manned spacecrafts to be launched at the Wenchang launch site in Hainan province, the salt fog, as a new environmental factor to aggravate the erosion, must be considered as a serious issue. This paper analyzes the impact of the salt fog on the manned spacecraft in the Hainan launch site. The salt fog level of the Hainan launch sate is investigated firstly. Then, based on the analysis of the mechanism of salt fog effect, and taking account of the characteristics of manned spacecrafts' development process, an engineering method combining the salt fog test with the active protection is proposed. The salt fog screening form given lastly may serve as a guide for spacecrafts launched at the Wenchang site with regard to the salt spray protection and the screening of sensitive factors.