Abstract: The moisture diffusion behavior of several types of domestic polymer matrix composites was systematically studied and their basic moisture diffusion parameters, such as the equilibrium moisture content M_m, the constants a and b in the relationship between M_m and relative humidity φ, the moisture diffusion coefficient in the direction of laminate thickness D_x, the constants ΔE(the active energy of moisture diffusion)and D₀ in the relationship of D_x and temperature T, were obtained.