The concept of ecological niche had remained as one of the core ideas in ecological research for almost a century, which was closely linked with interspecific competition, resource utilization had played an important role in the study of community composition and function,of the relationships among species,biodiversity,community succession and population evolution. Based on four seasonal investigations (Spring 2007, Summer 2006, Autumn 2007 and Winter 2006) in northern Beibu Gulf from 2006 to 2007, the niche breadth, niche overlap, spatial differentiation and environment effects on the abundance and spatial distribution of zooplankton were studied with qualitative and quantitative methods. The cumulative top 80% of zooplankton dominant populations were selected by the K-dominant curve method, then the niche breadths and their overlaps of zooplankton were measured using the formulas proposed by Levins Niche Breadth index and the Pianka Niche Overlap index, and the spatial niche differentiation was studied by using Detrended Canonical Correspondence Analysis (DCCA) method. The results showed that the zooplankton dominant species in northern Beibu Gulf were classified in to three groups, i e., wide niche breadth groups (B_i=0.60-0.77), middle niche breadth groups (B_i=0.30-0.60), narrow niche breadth groups (B_i=0.08-0.30) based on the niche breadth value. The niche breadths of zooplankton such as Sagitta enflata, Subeucalanus subcrassus and Macrura larvae were wider, which was related with their own characteristics and the capability of adapting environment, while the species whose niche breadths were narrower such as Doliolum denticulatum and Dolioletta gegenbauri will be considered as an indicative significance for ocean currents and water masses. Niche breadth could reflect the zooplankton abundance with the seasonal dynamic changes,and also could objectively reflect the species in the habitat in which the distributions of degree but it could not reflect the Accurate zooplankton abundance. The niche breadth values of dominance zooplankton species ranged between 0.08 and 0.77 in the whole year and The niche breadth difference among the dominant populations was great; The niche overlap values of dominance zooplankton species ranged between 0.02 and 0.89 in the whole year and the average niche overlap index was 0.45, there was strong complementarity in terms of the utility of resource among zooplankton populations, which had certain relationship with northern Beibu Gulf habitat diversification and the strong complementarity in terms of the utility of resource among zooplankton populations. The Detrended Canonical Correspondence Analysis result showed that depth, temperature and salinity had more important influence on the species spatial distribution than Chlorophyll a and dissolved oxygen.