Based on the functions of three-dimensional laser color scanner（3DLCS） developed by our research group and the practical require of police bullet identification

a new method called statistical algorithm based on grain distribution（SABGD） for automatic bullet trace detecting is given.SABGD uses a series of image process methods

such as edge detecting

noise deleting

and threshold division

and finds an image property which describes image grain distribution.By this property as well as traditional minimum absolute distance（MAD） algorithm we can do automatic bullet trace detecting.From the experiment results

we prove that SABGD can considerably alleviate the workload of human trace detectors and enhance the efficiency of related police jobs.