Abstract: The axial compression test was carried out based on 3 different size specimens of Fraxinus chinensis, Abies fabri and Pinus yunnanensis to explore the effect of specimen length on the variation of axial compression mechanical properties of coniferous and broadleaf woods along grain direction. The Weibull weakest link theory was used to calculate the length size effect coefficients of the compressive strength of 3 kinds of wood. The finite element software was used to simulate the axial pressure behavior of the wood specimen with the tested parameters. The results showed that the tested wood had a significant size effect on the compressive strength and peak strain of wood along the grain. When the specimen length increased from 40 mm to 80 mm, the average compressive strength of 3 wood specimens decreased by 4.10%, 7.19% and 5.78%. In contrast, the average peak strain decreased by 46.38%, 70.07% and 33.49%. The length size effect coefficients of compressive strength of F. chinensis, A. fabri and P. yunnanensis(0.06, 0.11 and 0.09, respectively) obtained based on the Weibull weakest link theory can be used for interconversion between the compressive strength tests of 3 woods with different test sizes. Based on the above coefficients to adjust the compressive strength of a specimen with a length of 100 mm, the error is only 0.76%, 1.9% and 1.06%. Based on the OpenSees fiber cross-section model, the nonlinear behavior of wood members under axial compression can be well simulated, but the impact of size effects on wood mechanical parameters needs to be considered.