A method was put forward to improve the wear resistance performance of nozzle by spraying surface coating on the sealing cone of needle.Based on the material requirement of nozzle,Al2O3 and DLC were selected as two kinds of representative surface coating.The contact stress distribution of diesel nozzles applied these two coating were analyzed using software ANSYS.The results show that strength,hardness,allowable stress and impact resistance of the needl〖JP5〗e’s〖JP〗ealing cone are significantly improved by Al2O3 and DLC coatings,and DLC coating has better protective effect on needle couples.With the increasing of coating thickness sprayed on the sealing cone of needle,the maximum contact stress of needle couples is reduced,the stress concentration is decreased and is transfered to the coating.Engine test was conducted to check the wear resistance of needle couples sprayed DLC coating.The results indicate that the wear resistance performance of needle is indeed enhanced after adding DLC coating.