By applying the principle of the MATLAB digital imaging technique, the images of surface defects on wood arch bridge components were enhanced, and the internal stress wave images were segregated and the defect areas were calculated. The effects of textural feature of defective pillars on the stress wave images were evaluated. The results showed that MATLAB software performed effectively on detecting the surface defects and analyzing internal stress wave images of the wood members. Based on area analysis of segregated areas and textural feature calculations of stress wave images, the pixel area and entropy value are proposed to be used as primary evaluation indexes for stress wave image analysis.