Abstract: Two kinds of submerged plants,tape grass and black algae,were selected as experimentalmaterials to investigate the effects of water depth on the removals of CODMn,total nitrogen and totalphosphorus. The results showed the removal rates of CODMn treated by tape grass and black algae for 14days at the water depth of 1.5 m were 52% and 56%,respectively. After treated by either of the twosubmerged plants for 12 days,the total nitrogen concentrations reduced to below 1.0 mg·L-1,and thenitrogen removal rates at 1.2 m were 13% and 20% higher than those at 0.3 m,respectively. After trea-ted by either of the two submerged plants for 8 days,the total phosphorus concentrations reduced to be-low 0.05 mg·L-1 at the water depth from 0.9 m to 1.2 m,and the total phosphorus removal rates weremore than 62%. The influence of water depth on the pollutant removal by submerged plants wasbecause of the growth of root and stem and the biofilm on plant surface. At 0.9 m and 1.5 m,the sur-face organic matter contents were 2.53 mg·g-1 and 2.72 mg·g-1 in fresh weight,respectively,whichwere both increased by about 12% and higher than that at any other water depths. The root lengths oftape grass and black algae at 1.5 m were 8% and 40% less than those at 1.2 m,respectively. As a re-sult,the removal effects of CODMn and total nitrogen did not change significantly at 1.5 m. The optimumplanting depth of tape grass and black algae was 0.9~1.2 m. Close-