In the production process of billet detection and recognition, how to accurately determine character string target location at the end of billet from the complex illumination scene is a key technical problem. In order to solve this problem, a method to complete character string location precisely is proposed. This method consists of Mean Shift restrain complex scene image, multistage segmentation filtering and clustering processing, and least squares trim angle adaptively for finding the character string interest area. The experimental results show that the location method cancomplete location precisely in various billet character string of complex scene and has better stability and accuracy than the traditional projector location method, and solve the location problem of billet character string on complex scene, and provide key technology in the billet character recognition of work.