Abstract:Larch dimension lumber of cross section size 40mm×90mm was chosen to be as the species. The dimension lumber was visually graded according to Chinese standard GB 50005—2003, and then full size bending test was carried out to establish the relationships between different mechanical properties and the grade boundaries for mechanical grading of larch dimension lumber were set. At the end, the mechanical grades of larch dimension lumber were obtained. Through visual grading, a higher proportion of high grade dimension lumber was received, and the major grade reducing defects of larch dimension lumber, such as knots, shake/check and decay were observed. With modulus of elasticity as indicator property, larch dimension lumber could be sorted into three grades: M14, M30 and M40. The grade strength of larch dimension lumber is in sequence as: M40, Ⅰc, M30, Ⅲc, Ⅱc, M14. The strength properties of mechanical grading dimension lumber were more stable, the value of lumber has been significantly improved. Through the comprehensive comparison, Chinese commercial forest of larch is more suitable for mechanical grading.