Abstract: In August 2020, the contents of 9 heavy metals (Zn, Cr, Pb, As, Cu, Cd, Ni, Fe, Mn) in the surface and subsurface (50 cm deep) sediments, interstitial water, and discharged wastewater of the Baimaohai tidal flat were determined, used the potential ecological risk index method and correlation analysis to analyzed the distribution characteristics, pollution risks and related relationships of heavy metals in the Baimaohai tidal flat based on the sediment grain size and TOC content. The results showed that the study area was mainly sand, with very little clay and chalk, of which the average TOC content was 0.031%, the content of heavy metals was Fe>Mn>Zn>Cr>Pb>As>Ni>Cu>Cd. Along the coast, there was an enrichment tendency for heavy metals in the P1 profile where the content of some heavy metals exceeded the average expectation. The distribution of heavy metals in surface sediments along the vertical direction was no obvious regularities. The content of Pb, Zn, Cu, Cr, As, Cd in the sediments at different depths were all below the permissible values of the class-I marine sediments(China Marine Sediment Quality Standards). The content of heavy metals in interstitial water was Mn>Fe>Zn>As>Ni>Cu>Pb>Cr>Cd, and for Cr, Fe, and Mn, their contents in the different mediums were significantly different. In the study area, the redox metals had a great influence on the content of heavy metals, while the grain size and TOC had a little influence. The value of comprehensive potential ecological risk indexERI was 113.03, which belonged to the category of minor ecological potential risk. The potential ecological pollution degree of each element was Cd>As>Pb>Cu>Zn>Cr. Cd was the main pollution factor in the surface sediment of the study, which should be listed as the priority element to be controlled in the tidal flat at the Baimaohai.