This paper presents the new research achievements and experiment results of the application of 500 W CW YAG laser quenching for engine cylinder block, and then analyses the advantages of YAG laser quenching compared with C〇₂ laser quenching. In computer controlling system, the concept of horizontal diamond number and vertical diamond number is proposed, new mathematics model is derived, and derived new technique of locally densified mesh is put forward. Laser quenching in high precision mesh is realized by software controlling .