The wood failure percentage is an important indicator to characterize the glued performance of glulam beams and wood-laminated timber. In this study, a fast digital measurement method of CLT wood failure percentage based on grayscale and color image processing was proposed. In order to verify the feasibility of this method, the shear failure samples prepared with larch and carbonized bamboo as the base material and PF and MDI as the adhesives were tested under dry and wet shear conditions. The wood failure percentage calculated by the experimental method and the gray-scale and color image processing methods are in good agreement with the experimental values, and the errors meet the requirements of engineering applications. However, the color change of the wood damage level and the wood failure percentage image has a greater impact on the measurement accuracy. Among them, the change of the inherent color of the adhesive has a greater impact on the accuracy of the threshold segmentation gray-scale wood failure percentage image measurement method, while the environmental impact It is the main factor of the color wood failure percentage measurement method of pixel statistics.