Chlorophyll a (Chl a) concentrations and primary productivity were investigated in the surface water of the Nan'ao-Dongshan coastal area in September (autumn) and December (winter) of 2014, April (spring) of 2015, and July (summer) of 2017. The seasonal and spatial distribution patterns of Chl a and primary productivity were analyzed. The Chl a concentration varied from 0.37 μg/L to 14.9 μg/L. The average Chl a concentration in the surface water were summer (8.2 μg/L) > autumn (4.9 μg/L) > winter (1.52 μg/L) > spring (1.47 μg/L). The primary productivity varied from 0.6 to 45 mg(C)/(m³·h), and the average values were autumn[20.3 mg(C)/(m³·h)] > summer[18.2 mg(C)/(m³·h)] > spring[14.4 mg(C)/(m³·h)] > winter[5.6 mg(C)/(m³·h)]. The depth-integrated primary productivity varied from 14.1 mg(C)/(m²·d) to 3066.6 mg(C)/(m²·d), and the average values were autumn[1034.2 mg(C)/(m²·d)] > summer[715.5 mg(C)/(m²·d)] > spring[453.4 mg(C)/(m²·d)] > winter[133.8 mg(C)/(m²·d)]. The Chl a concentration generally decreased from the northwest inshore region to the southeast offshore region during the four seasons. However, there was no clear pattern for the distribution of primary productivity. Significant correlations between Chl a, primary productivity, and nutrients were found only in spring. Nitrogen may be a relatively important limiting nutrition factor in the Nan'ao-Dongshan coastal region. In general, the water quality was healthy and the concentrations of Chl a and nutrients were relatively low. For the sustainable utilization of fishery resources, a reasonable plan regarding stocking densities is needed for the cultured species according to the primary productivity in the Nan'ao-Dongshan costal region.