Abstract: The survival rate，sex ratio，fecundity，index of population trend of natural population of Spodoptera litura of the 4～5th generations are studied and the control function of natural enemies on the natural population of Spodoptera litura is analyzed by means index of population control(IPC)．The results show that the hatching rates of Spodoptera litura of the 4～5th generations’egg are 88．34％ and 89．33％ ，and the survival rates of pupa are 57．74％ and 61．48％ ，and the survival rates of larva are 0．78％ and 0．63％ ，and the sex ratio of adults is 1：1 around，and the numbers of egg oviposition are 1723 and 1477 granules per female，and the indexes of population trend are 3．145 and 2．31，respectively．The control function of spider is the largest on the population number of Spodoptera litura，and indexes of population contro1 are 12．83 and 9．06，disease and natura1 death are secondly，IPCs are 4．54 and 6．33．