The Mahalanobis distance feature proposed by P.C Mahalanobis, an indian statistician. In this paper, we propose a new concept, Local Region Mahalanobis Distance feature -LRMD feature, we shall discuss the structure form, the obtaining methods of LRMD feature from an image and the relations between the LRMD feature and wearing and breakage states of cutting tools. The new research results indicate that the method of automatic on-line cutting tool condition monitoring based on LRMD feature can has better inspect result than the method of Mahalanobis Distance feature.