Abstract: The key technique of on line laser quenching manufacture for automobile engine cylinder is studied and laser resonator construction,optical elements and cooling technique are improved.Aqua metal oxide colloid absorbency is developed,to form absorb light coat on line is realized with the help of precision hole spurt out method.Based on the above technique,an engine cylinder laser quenching numerical control machine is developed.The machine is an optical,mechanical,electrical modular system.It is the first time for automobile engine cylinder is quenched on line in China.