The wetting contact angles of various liquids on the bamboo surface were measured with the apparatus for contact angle measurement, the surface free energy of bamboo was calculated with the Zisman formula, the effect of aging on the wettability of bamboo was analysed with the ESR. The results show taht: the surface free energy of bamboo is approximately 0. 0535 J·m-2 and is similar to most parts of wood; surface aging can make the number of free radical decrease and cause the decrease of the wettability.