It is important to know strength performance of sugi(Cryptmeria japonica D.Don.) in order to produce engineering wood products efficiently. In this study, distribution of dynamic modukes due to longitudial vibration method (Efr), that it is nondestructive evaluation method, of the sugi logs grown in Oita prefecture was grasped. And the posibilities of stress granding by sugi cultivar and visual observation, etc. were also verified, and the practical stress granding methods in the field were examined. The result are summarized as follows: (1)The mean value of Efr of the sugi logs (n=3935) grown in Oita Prefecture was 7.70GPa(CV:25.0%). (2)The mean value of Efr of the sugi middle diameter logs was 6.31GPa(CV:25.4%) and the first logs was 5.33GPa(CV:21.4%), and logs except for the first logs was 7.02GPa(CV:21.6%). All logs except for the forst logs showed about 1.3 times the value of the first logs. (3) Efr of sugi middle diameter logs in the wood market in oita prefecture was the almost equal to the values of Kumamoto and Kagoshima preefctual test deta. From this fact, it was estimated that the mean value of dynamic modules of the sugi middle diameter logs grown in Kyushu is about 6～7GPa. (4) The values of Efr varied with sugi cultivars. And also, values of Efr of the first logs in the identical stand tree ware lower than the uppre logs. The rough estimation of Efr is possible, if sugi caultivar and classification by the log sequences are clarified. (5)Distribution of Efr of logs grown in Oita prefecture was considered to fluctuate, with the combination of sugi cultivar, stand age and growth condition. So it is important to construct the detabase in the forest management which include the sugi cultivar, stand age and growth condition etc.. (6)It was found that the visual classification from taper rate and average width of annual rings in possible to estimate Efr approximately. However, Efr had the higher correlation with natural frequency than the visual indexes taper rate and average width of annual rings. So, it could be thought that Efr estimated with natural frequency is aimple and practical index for the stress grading.