Abstract: Graphene oxide (GO) modified carbon fiber/epoxy resin (CF/EP) composites were prepared by wet prepreg technology and molding process. The effects of GO on dynamic mechanical properties and interlaminar shear properties of the GO-CF/EP composites at room temperature and hygrothermal environment were studied. Micro morphology was used to analyze modification mechanism of the GO-CF/EP composites. The results show that when the addition amount of GO are 0.5% and 0.8%, respectively, the glass transition temperature (T_g) of the GO-CF/EP composites are significantly increased from 184.4℃ of the CF/EP composites to 197.7℃ and 199.5℃, respectively. After hygrothermal treatment, T_g retention rate of the GO-CF/EP composites is slightly lower than that of the CF/EP composites. The interlaminar shear strength of GO-CF/EP composite with GO content of 0.05% and GO-CF/EP composite with GO content of 0.1% are increased from 59.7 MPa of the CF/EP to 70.2 MPa and 72.2 MPa, respectively. The interlaminar shear strength after hygrothermal treatment of GO-CF/EP composite with GO content of 0.05% and GO-CF/EP composite with GO content of 0.1% are improved compared to the CF/EP composite. And the interlaminar shear strength retention rates of the GO-CF/EP composites before and after hygrothermal treatment are all lower than the CF/EP composite. Dynamic mechanical loss analysis of the composites shows that GO effectively improves the interface bonding between CF and EP matrix. Micro morphology shows that the existence of GO improves the ability of GO-CF/EP composites to resist crack growth.