In order to determine the shear strength parallel to grain for small-diameter logs or thin lumber, this paper describes a new test method in which the width of the specimen was cut to half its standard size. The feasibility of using the modified shear specimen, as a substitute for a standard specimen, was determined by comparing the shear strength between modified and standard （specimens） from both Chinese Fir （Cunninghamia lanceolata） and Poplar I-214 [Populus × euramericana （Dode） Guineir cv.’I-214’] lumber. Results showed that the absolute values of the relative differences of the shear strength between the standard and modified specimens for matched （condition） were under 3%, and there was no significant difference at the 0.05 probability level. This provided a useful method for measuring the shear strength parallel to the wood grain for small or undersize timber.