Abstract: Sanggou bay is an important semi closed demonstration zone of large-scale mariculture in China. Heavy metals are a kind of pollutants, which are highly toxic to environment and organisms. It is, therefore, highly essential and urgent to investigate the pollution status and seasonal variation of heavy metals in the surface seawater of Sanggou bay. It will make great contribution to mariculture activities and be ecologically important for the preservation of marine ecosystem in Sanggou bay. In this study, we thus collected surface seawater of 21 stations in spring (April), summer (July), autumn (October) and winter (December) in 2019, respectively. We then determined the concentrations of Cu, Zn, Pb and Cd in the surface seawater, and analyzed subsequently their seasonal variation, distribution characteristics and pollution degree. The results showed that the concentrations of Cu, Zn, Pb, Cd were in the range of 1.14～2.88 μg/L, 4.62～6.53 μg/L, 0.38～1.55 μg/L and 0.18～0.92 μg/L, respectively. Generally, the concentration of the four heavy metals appeared to increase and then decrease from west to east of Sanggou bay. Single factor pollution indices showed that the order of the pollution degree of the four heavy metals was Zn < Cu < Cd < Pb. There were also seasonal variation and culture area differences of heavy metals concentration and pollution degree, leading to the higher level of the four heavy metals in summer and shellfish algae mixed culture area. However, the concentration and pollution degree of the four heavy metals in the surface seawater of Sanggou bay is approximately equal to and/or even much lower than those of many other mariculture areas in China. Overall, the level of the four heavy metals in the surface seawater of Sanggou bay is in the clean level and in line with the national first-class seawater quality standards. We therefore conclude that the seawater quality of Sanggou bay is very suitable for mariculture.