Water samples were collected in the northern, eastern and southern tidal creeks of Chongming Dongtan in January, 2009. The samples were passed through 0.45μm pore size GF/C glass fiber membrane and colloid was isolated by mini tangential flow ultrafiltration (TFF) with ultrafiltration membrane pore-size of 1kD (1kD=1 000 Daltons). Then the content of organic carbon was tested by TOC II. Results show that the contents of dissolved and colloidal organic carbon (DOC and COC) in the northern creek are higher than the eastern and southern tidal creeks of Chongming Dongtan, and the concentration of DOC decreased from high tidal flat to low tidal flat. Hydrodynamic and vegetation are the important factors to affect the content of COC in tidal creek water of Chongming Dongtan.