Threshold selection is very important for image segmentation. How to get fine threshold is an old

but difficult problem in image processing. We have to make new method for threshold selection in some image analysis because all threshold rule have been put forward for image segmentation can't work well for all images. A pattern about making the method for threshold selection is put forward in this paper. Application in many old methods and some new methods show how to use it to get a new method for threshold selection in practice.