Two kinds of submerged plants,tape grass and black algae, were selected as experimental materials to investigate the effects of water depth on the removals of CODMn, total nitrogen and total phosphorus. The results showed the removal rates of CODMn treated by tape grass and black algae for 14 days at the water depth of 1.5 m were 52% and 56%, respectively. After treated by either of the two submerged plants for 12 days, the total nitrogen concentrations reduced to below 1.0 mg·L-1, and the nitrogen removal rates at 1.2 m were 13% and 20% higher than those at 0.3 m, respectively. After treated by either of the two submerged plants for 8 days, the total phosphorus concentrations reduced to below 0.05 mg·L-1 at the water depth from 0.9 m to 1.2 m, and the total phosphorus removal rates were more than 62%. The influence of water depth on the pollutant removal by submerged plants was because of the growth of root and stem and the biofilm on plant surface. At 0.9 m and 1.5 m, the surface organic matter contents were 2.53 mg·g-1 and 2.72 mg·g-1 in fresh weight, respectively, which were both increased by about 12% and higher than that at any other water depths. The root lengths of tape grass and black algae at 1.5 m were 8% and 40% less than those at 1.2 m,respectively. As a result, the removal effects of CODMn and total nitrogen did not change significantly at 1.5 m. The optimum planting depth of tape grass and black algae was 0.9~1.2 m.