The invention relates to a chromium-ceramic composite coating reticulate crack quantitative detection method and belongs to the metallographic structure quantitative technique field. The method comprises the following steps that: mechanical grinding and mechanical polishing are sequentially performed on a chromium-ceramic composite coating sample until the surface of the chromium-ceramic composite coating sample is smooth and becomes a mirror surface; the chromium-ceramic composite coating sample is arranged in a scanning electron microscope, image brightness and contrast are adjusted, and the crack picture of the surface of the sample is acquired; preprocessing and graphics segmentation are performed on the crack picture, and a crack region in the picture is extracted; and the crack region is analyzed, the area percentage data of crack density in the chromium-ceramic composite coating sample is calculated. According to the method, the preprocessing method and the graphics segmentation method are adopted to extract the crack region in the picture, and therefore, the percentage of the reticulate crack of the chromium-ceramic composite coating can be quickly and accurately analyzed.