The work deals with the diffusion of low-molecular substances – water – in CFRP gravimetric method and the method of determining the concentration of water layering. Detected non-Fickian character moisture sorption process and fikovsky – desorption. Established time dependence of the diffusion coefficient. Identified anomalies are due to relaxation phenomena in the process of penetration of water into the polymer composite. The effect of temperature on the diffusion characteristics of the carbon fiber and is designed activation energy.