BY using direct scanning method, the accuracy of wood microdensitometry with 3 kinds of x-ray source ((55)~Fe, (238)~Pu and x-ray tube) was studied and the Variation of mass attenuation coefficients of 4 species of wood was determined and analized The measurement with (55)~Fe and x-ray tube was found more accurate than that with (238)~Pu because the x-ray energy of the formers is closer to the optimal one than the latter A certain degree of variation of wood mass attenuation coefficienat among species and within a species was showed in the tests, which should be considered as high accuracy of the measurement is expected