Abstract: The wear of dismond tools has been studied. The SEM observation has shown two kinds of wear including mild wear and severe wear. The mild wear involves grooved wear,delamination wear and spot etching, while the severe wear covers crack wear, squeezins and seperating interface matrix and diamond,breaking off of whole dismond,etc. The cause and mechanism of the production of various forms of wear have been analysed. It has been bound that the height above the edge of diamond tools decreases with mild wear but increases with severe wear(Though the severe wear of diamond can present a higher grinding efficiency,it diminishes tools' lifetime.