External nutrient reduction does not necessary lead to a quick recovery of eutrophic lake ecosystems. One of the main reasons is the nutrient release from sediments where phosphorus and nitrogen have been accumulated during long-term nutrient pollution. Lanthanum modified bentonite (Phoslock®) can effectively control the release of internal phosphorus in sediments, which is applied to restore the eutrophic lakes. Vallisneria denseserulata is a common submerged plant in shallow lakes in China, often used in lake ecological restoration projects. However, the interaction between sediment with Phoslock® treatment and water nutrients on submerged plants are less clear so far. Our study set up two treatments with and without the addition of Phoslock® in sediment, under two different nutrient concentration conditions in the overlying water. To investigate the interaction effects of Phoslock® and water nutrients on the growth and morphological of V. denseserulata. Our results showed that adding Phoslock® in sediments has a significant inhibitory effect on the growth of V. denseserulata. This inhibitory effect decreases as the nutrient contents in the water increases. The interaction effect of Phoslock® and water nutrient concentrations were detected in the underground biomass of V. denseserulata. Adding Phoslock® promoted the length growth of the roots. This phenomenon is more significant when the water nutrient lower.