The management of water pollution has been one of the main problems as people pay more and more attention in the current society to the preservation and repair of the natural environment. In this paper, natural montmorillonite was modified with starch as well as lanthanum chloride. The removal efficiency of various modified montmorillonites on pollutants was examined by simulating the water quality conditions of heavily polluted lake reservoirs in order to provide new eco-friendly and effective materials for the treatment of heavily polluted lakes and reservoirs. The experimental results showed that: The nitrogen removal rates of Na-Mont, St-Mont, La-Mont, St-La-Mont and La-St-Mont for 2 mg/L TN solution were 28.48%, 5.18%, 59.55%, 98.39%, 64.73%, respectively, and total phosphorus removal rates for 10 mg/L TP contaminated solution were 6.24%, 4.16%, 87.41%, 93.66%, 91.58% and for 100 mg/L COD solution the removal rates were 32.37%, 41.46%, 51.68%, 86.89%, 77.8%, respectively. By exploring the effect of La6-Mont adsorption for Cr6+ removal at different temperatures as well as reaction times, the results showed that the Cr6+ removal at saturation of La6-Mont adsorption was 76%, 80.5%, and 82.5% at the reaction temperatures of 15℃, 25℃, and 35℃, respectively. Among them, the removal rates of St-La-Mont reached more than 85%, 50% and 70% for COD, TN and for TP, respectively, and can be applied as fillers for enhanced artificial fast infiltration systems. The light rare earth composites La-St-Mont and LaCl3-Mont have achieved removal rates of 35%, 50% and more than 90% for COD, TN and for TP, respectively, and can be used as effective purification materials for treating water quality of heavily polluted lakes and reservoirs. Meanwhile, La6-Mont can effectively fix heavy metal ions and avoid the release of endogenous pollution in the bottom mud, which can be used as a material for the treatment of bottom mud in lake reservoirs. This shown that lanthanum, a light rare earth element, modified montmorillonite can not only remove a range of pollutants from water bodies but also has excellent removal rates. Additionally Besides, starch, lanthanum and montmorillonite are widely available materials with high economic benefits. Therefore, further studies on St-La-Mont, La-St-Mont, LaCl3-Mont and La6-Mont can provide new materials for the treatment of pollution in heavily polluted lakes and reservoirs.