Mechanisms in controlling the growth of heterotrophic bacteria have seldom been explored in the tropical South China Sea (SCS). This study report the tempo-spatial distribution patterns and the controlling mechanisms of bacterial biomass (BB), production (BP) and specific growth rate (Bm) from one summer (Jun, 2010; 4 transects) and two winter (Jan and Dec, 2011; one transect each) cruises along the northern SCS-shelf. In summer, all three bacterial variables showed strong gradients with greater readings at the inner-shelf then decreasing seaward. The positive correlations of bacterial production rate (BP) and bacterial specific growth rate (Bμ), with primary production (PP), chlorophyll-a and dissolved organic carbon observed in summer indicate a high possibility of bottom-up (substrate supply) control. Positive bacterial temperature response was observed in the inner to mid-shelf area in winter. There, Bm changed proportionally with temperature up to ca. 22 oC. The Q10 (the increase of reaction rate for a T rise of 10oC) for Bm was ~4.0, which was in the range reported by coastal studies. Very high BP/PP ratios (summer average: 89±92%; winter average: 131±88%) indicated bacteria carbon demand relied heavily on allochthonous organic carbon sources such as river input and re-suspension processes, and that the SCS-shelf might be net heterotrophic in these two seasons. In winter, BP/PP ratios changed positively with temperature in areas inside the mid-shelf, suggesting that the coastal zone might become a stronger CO2 source during cold season under a warming climate, if anthropogenic loadings of inorganic nutrients and organic matter remain high in the future.