One new binarization method for gray images is presented in this paper by defining the decision rule, which puts not only much emphasis on local approach but also completely incorporates the shape-feature of the objects in the images, especially for the shape of the object in the gray images is known in advance. Experimental results demonstrate that our proposed method is generally capable of dealing with binarization challenges with high performance and is effective in solving problems of low contrast between the foreground and the background.