Abstract: For the protected polymers in aerospace,the surface change of organic protective coatings in the vacuum ultraviolet radiation was investigated.The results show that VUV irradiation makes organic coatings produce mass loss,whose amount is in large quantity at initial stage and does not almost increase again as the extension of exposure.It is obviously that color of organic coatings except Siloxane have great change.So Siloxane is better in resistance to photo-aging than the others,VUV irradiation can case scission of various chemical bonds in polymers,for example,C-N,Si-CH_3,C-C,epoxy ring,but others such as SI-0,benzene ring,C=O are relatively stable under the environment of VUV irradiation.