NOVELTY - Fixing heavy metals in waste composting using impermeable layer, comprises: (i.a) preparing PVC pipe and fixing nylon mesh, and (i.b) filling dry soil, setting barrier layer and paving dry compost on the pipe; (ii.a) sowing Festuca seed, and (ii.b) applying nitrilotriacetic acid sodium salt solution to the compost surface; and (iii.a) applying EDTA, mowing Festuca, drying, and watering, and (iii.b) pouring artificial rain into each pipe, collecting percolate, measuring volume, applying EDTA, mowing, rinsing with artificial rainwater, and measuring the amount of heavy metal.    USE - The method is useful for fixing heavy metals in waste composting using impermeable layer.    ADVANTAGE - The method applies waste compost on the soil before setting the isolation layer to reduce the heavy metal in the compost underlying soil; utilizes chelating agent along with phytoremediation and adds isolation layer to purify the waste compost or soil polluted by heavy metals; and is environmental-friendly.    DETAILED DESCRIPTION - Fixing heavy metals in waste composting using impermeable layer, comprises: (i.a) preparing a PVC pipe with a diameter of 7.5 cm and length of 21 cm, fixing the bottom of the pipe with a nylon mesh with a diameter of 0.2 mm to support the soil and compost in the pipe, lifting the pipe and connecting a container filled with filtrate at the lower part of the pipe, and (i.b) filling dry soil (500 g) into the PVC pipe, setting a barrier layer in the middle and paving the dry compost (280 g) on the pipe, where the barrier layer is composed of three layers, a lower zeolite layer (20 g), an upper rice straw layer (20 g) and a middle colloid particle layer (40 g) with a particle size of 2 mm, egg shell or vermiculite; (ii.a) sowing Festuca seed (0.6 g) in the PVC pipe, using tap water to irrigate the PVC pipes, where the field water of the mixture of the compost and the soil is 60-65%, and maintaining the temperature at 16-22 degrees C and a relative humidity at 36-57%, and (ii.b) applying nitrilotriacetic acid sodium salt solution (150 ml the 5-15 mmol/kg of the compost) to the compost surface after 30 days of seeding; and (iii.a) applying EDTA after 10 days, mowing Festuca, maintaining stubble 1 cm, introducing the plant at 80 degrees C an oven for drying to constant weight, watering to maintain the constant moisture content in the watering pipe, and (iii.b) continuously and slowly pouring the artificial rain (150 ml equivalent to 34 mm of the precipitation) into each PVC pipe respectively after 2, 8 and 15 days of mowing, collecting the percolate at the bottom of the tube, grading and measuring the mixed volumes, applying EDTA on the 20th day, mowing, rinsing with artificial rainwater (150 ml) after 2, 8 and 15 days of mowing, collecting, and measuring the amount of heavy metal.