Abstract: Carbon fiber reinforced polymers (CFRP) were widely used in marine environments due to their corrosion resistance, light weight and high strength, and thus were subjected to hygrothermal environment for a long time. To understand the effects of hygrothermal environment and extreme temperatures on carbon fiber reinforced vinyl resin composites, the changes of compression properties, in-plane shear properties and interlaminar shear strength of CFRP before and after hygrothermal aging and at different testing temperatures were determined. The results of Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) show that the pure resin specimens undergo hydrolysis in the hygrothermal environment, which cause the microcracks and pores on the surfaces of the specimens to expand and penetrate into the interior of the specimens. The moisture absorption curve of CFRP is in high agreement with Fickian model, while the moisture absorption curve of pure resin deviated from Fickian model because the hydrolysis reaction affected the moisture absorption channels. Meanwhile, the measurement on mechanical properties reveals that the compressive strength and interlaminar shear strength decrease by 7.6% and 12.3%, respectively, after hygrothermal aging for 90 days, and the compressive strength, in-plane shear strength, and interlaminar shear strength of the specimens at elevated temperature (70℃) decrease sharply by 36.2%, 26.9% and 37.4%, respectively. Meanwhile, it can be concluded that the effect of elevated tempera-ture on the mechanical properties of the specimens is partially reversible.