The Nanji Islands marine conservation area is one of the first five national marine nature reserves established in China with the approval of the State Council. Because it has a reputation for marine life, and especially for its abundance and variety of shellfish and algae, it is called the "kingdom of shellfish and algae". It is an excellent place for the spawning, feeding, and growth of fish and shrimp, but few scholars or experts have studied the species composition and quantitative distribution of shrimp in the Nanji Islands marine conservation area. We collected shrimp data based on comprehensive fishery resource surveys in November, 2013, and in February, May, and September, 2014, in the Nanji Islands marine conservation area. We studied the species compositions, quantitative distributions, trends in dominant species, and their relationships to environmental factors affecting shrimp in the Nanji Islands marine conservation area, according to survey data for the four seasons, and used catch rates as a quantitative index of the shrimp resource distribution. (1) A total of 25 species were identified, from 74 genera in 49 families, and the seasonal shrimp biomass was (in decreasing order) summer (32358.0 g) > autumn (13033.0 g) > winter (3938.6 g) > spring (3635.6 g). (2) The seasonal change in the distribution of the shrimp population is clear, and the shrimp biomass in reef areas outside the open ocean was considerably higher. (3) The seasonal variation in the dominant species, or the seasonal succession phenomenon, was very obvious, and the dominant species were Parapenaeopsis hardwickii in spring; H. ensirostris, Exopalaemon carincauda, in winter. (4) The depth of the water clearly affected the vertical distribution of the shrimp biomass and the correlation relationship has greatly changes between the shrimp biomass and environmental factors in different seasons. According to our research,the shrimp species mainly belonged to seasonal, eurythermic, and euryhaline groups. The biomass of the dominant shrimp species was clearly higher in the summer and autumn than in the spring and winter, perhaps because many shrimp leave the area for other waters to breed in spring and winter, but return to the sea to spawn, fatten, and grow in summer and autumn. The shrimp biomass in the coastal area exceeded that in the reef and gravel areas in summer, autumn, and winter, perhaps because the shrimp live their general lives in the bottom silt of coastal areas, which benefit to bait and grow up. The replacement of dominant species was significant, and was related to the growth cycles and different size characteristics of the main dominant species. The shrimp biomass has complex relation with environmental factors because the characteristics of the Nanji Islands marine conservation area are complex, with changeable salinity and temperature and diverse fauna. The distribution of the shrimp biomass clearly changed with depth, which was mainly attributable to the range of activities of the dominant species, which are related to the depth of the water in the survey area.