Abstract: In order to investigate the effect of different parts (North or South) and radial directions (Near pith or near bark) on the mechanical properties and air-dried density of plantation wood, the mechanical properties and air-dried density of plantation-grown Castanopsis hystrix and Betula alnoides at different parts and radial directions were studied.The effect of the two factors mentioned above on the mechanical properties, air-dried density and the correlation between wood density and three main mechanical properties (bending strength, modulus of elasticity in bending, compressive strength parallel to grain of wood) were discussed and analyzed.The results show that there is no significant difference for most mechanical properties and air-dried density between the samples from north and south directions for both species.However, significant differences of shearing strength parallel to grain of tangential face, nail hold ability of radial direction, and surface hardness of three faces, between the samples from north and south directions are observed for C.hystrix and B.alnoides.There is no significant difference for the three main mechanical properties and air-dried density between the samples from near pith and near bark for C.hystrix, while the significant difference is found for B.alnoides.There is remarkably positive correlation between air-dried density and wood mechanical properties for both species.