The authors sought to establish a method to determine characteristic strength of structural wood materials by using the nonparametric method, to provide a scientific basis for safety design and reasonable application in wood building structures. Characteristic strength was a key mechanical property index for structural wood materials, which was determined by confidence level requirements. Random samples generated by a normal distribution were used to investigate relationships among confidence level and coefficient of variation of sample’s strength, specimen numbers in sampling, as well as statistical order for characteristic strength. Minimum number of specimens at different confidence levels and statistical order were obtained. A calculation formula for the statistical order was then developed.