Abstract: Several problems between biodiversity and dynamics of population quantity are stated.The ecological mechanisms between plant diversity and quantity dynamics of pest population mainly are natural enemies hypothesis and resources centralization hypothesis while in studies of metapopulation theory,mathematical models play leading roles.This theory makes much sense in studies of both landscape ecology and protective biology.Disturbance also plays a primary role during the course of forming an ecosystem through producing temporal and spatial incrustation under different and continuous states ,and medium degree of disturbance can preserve a high diversity.Genetic diversity researches have experienced four stages of morphological level,chromosome level,physiological and biochemical level,and molecular level.The four methods both have their advantages and disadvantages and can not be replaced by each other.Biodiversity within different ranges can be increased by protection of biodiversity,and can increase the stability of the population and function of ecosystem.