Abstract: Based on the studies of life tables of diamondback moth (DBM),Pbatella xylostella (L.),"perasitization" at the pupae stage were established as the most important mortality factor for the population of DBM.The new style of insecticides (chitin synthesis inhibiting insecticide) IKI-7899 which was sprayed at the concentration of 50 ppm were promised to be favourable to the parasites,and could provide effective control of the DBM,with 98.80%of the control efficency for the larvae and 0.0009 of the population trend index (I),while conventional insecticides cypermethrin (200 ppm) and dichlorvos (1600 ppm),which were mixed used for four sprays at an interval of 4-5 days,in the whole generation were harmful to the enemies and could not effecctively control the DBM,with 62.82% of the control efficency and 9.2769 of the trend index (I).