Abstract: The ocean primary productivity (OPP) is a great basis for ocean ecology assessment, which qualify important significance for ocean resources exploitation. Based on Vertically Generalized Production Model(VGPM), the primary productivity in the Beibu Gulf, China, was estimated using the MODIS ocean color products and in-site water monitoring data. Temporal and spatial variation characteristics and correlation of environmental factors which impact the OPP in the mechanism of phytoplankton growing was given in this study. The result indicated a higher OPP in spring and winter, and lower OPP in summer and autumn of the whole year; and the OPP was higher in the nearshore compared with the offshore. The average OPP showed a peak in December as 2196.23 mg C/(m²/d) and a trough in August as 693.73 mg C/(m²/d); OPP is negatively correlated with photosynthetically active radiation (PAR) and SST, and positively correlated with sea surface salinity (SSS). And the study about the effect of nutrients on primary productivity shows the demand for nitrite is not high for phytoplankton in Beibu gulf, while orthophosphate is more obvious.