Abstract:The scale insect Quadraspidiotus perniciosus(comstock)is one of the important pests of jujube．In Shanxi Province，this insect has two generations a year and overwinters as 2nd instar nymph of the 2nd generation on the branch．The overwintering nymphs begin to harm the host in late March the following year．The nymphs of male and female have two instars．The adults of the second and the first generations emerge in early May and in mid-July，respectively．The sex ratios of the two generations are 1:0.26 and 1:0.35，respectively．The ralationship between the population density and natural death rate and the different parts and directions of the host plant are also investigated． Besides，the distribution of the nymphs on the jujube leaf，the effect of the branch age and the density of the pest on the fluctuation of the population，the forecasting to the occurance of the nymphs and adults，and the temperature and moisture on the development of the pest．And the methods of control are also studied．