Abstract: The seawater samples were collected in Yellow Sea and Bohai Sea. The DGM of surface, middle and bottom seawater was measured. Variation and differences of DGM in the coastal, open sea and estuarine areas was studied. The results showed that DGM concentration in the surface layer and bottom layer of the nearshore site was much higher (160~230 pg/L, 160~250 pg/L) than that in the middle layer (50~140 pg/L). The DGM concentration in the bottom seawater was higher in coastal sites with high turbidity because sediment resuspension was helpful to the release of DGM from the sediments to the upper seawater. At open sea, DGM in the surface layer and middle layer was higher (140~210 pg/L, 130~200 pg/L, respectively), than that in bottom (60~180 pg/L). DGM in clean surface water was mainly produced by light reduction, while the DGM of the bottom seawater came from the diffusion of the upper DGM or the release of DGM from the sediments. The DGM concentration was high in the surface sea water near the estuary of the Yangtze River and Yellow sea, the concentration of DGM decreased following the increase of depth. The lower DGM at the bottom of the estuary indicates that less DGM produced in the bottom sediments. The high concentration of DGM was not found in the hypoxic region of the Yangtze estuary, indicating that the hypoxia might not be benefit to DGM production.