Abstract: Based on the data obtained in summer, autumn, winter and spring in Qinzhou Bay and its adjacent waters in 2013-2014, the temporal and spatial variations of dissolved heavy metals in surface seawater and the factors affecting the distribution of heavy metals are studied with principal component analysis. The results show that the contents of Cu, Pb, Zn, Cd, Cr, Hg and As are in ranges of 0.214-1.510 μg/dm³, less than 0.979 μg/dm³, 0.132-4.160 μg/dm³, 0.005-0.106 μg/dm³, 0.014-2.580 μg/dm³, 0.012-0.049 μg/dm³ and 1.2-2.2 μg/dm³, respectively. The contents are low compared with the data from literatures. The average contents of heavy metals in summer and autumn are in order of As > Cu > Zn > Cr > Pb > Cd > Hg, while in winter and spring they are in order of As > Zn > Cu > Pb > Cr > Cd > Hg. The concentrations of copper, zinc, cadmium, mercury and arsenic in rainy season are usually higher than those in dry season because the runoff to the sea is controlled by the precipitation. The atmospheric deposition during the northeast monsoon period may be the reason for an increasing lead content from summer 2013 to spring 2014. The homology among heavy metals is significant except for lead and cadmium in summer, and lead, cadmium and zinc and cadmium and zinc in winter. Terrigenous input is the most important source of heavy metals in Qinzhou Bay and its adjacent sea areas. The process of adsorption and desorption by change of pH and physical mixing of saltwater and freshwater are the main factors affecting the distribution of heavy metals. Besides, the strong tidal current is another important factor affecting the distribution of heavy metals.