The invention relates to a coal mining subsidence water area heavy metal treatment method, aiming to solve the problem that subsidence water areas away contain excess heavy metal such as copper, cadmium, lead and zinc and some of the subsidence water areas are communicated with underground mine water, which are difficult to treat. The coal mining subsidence water area heavy metal treatment method includes the steps of cultivating sub-mature field snails specially, breeding the field snails in the subsidence water areas until the field snails are mature one month later; fishing the mature field snails and smashing the same, mixing the smashed field snails with water and quick lime to form ecological concrete, feeding the ecological concrete to cracks, steps and pits of the subsidence water areas, and finally covering the cracks, the steps and the pits of the subsidence water areas with clay and tamping the clay to form water-tight layers. Therefore, the water-tight layers for the subsidence water areas can be formed within a short time, and the field snails which are cultivated specially and capable of gathering the heavy metal are closed in the water-tight layers finally so as to control the heavy metal reliably. The coal mining subsidence water area heavy metal treatment method has the advantages of being effective and thorough in treatment, can close the excess heavy metal thoroughly and improve the coal mining subsidence water areas into utilizable water areas with high-quality and stable water, and is applicable to early treatment of the coal mining subsidence water areas widely.