The coating is one of the most important auxiliary materials of lost foam casting. In order to reduce the cost of coating for lost foam casting, water based coating has been developed. Refractory material of quartz sands that have three kinds of grain size distribution was used. All coatings were made into paste form by sand roller mill. The paste form was stirred into liquid coating by adding some water in stirrer, then measuring their properties. The developed coating has relative concentrated grain size distribution and consists of quartz sand 100%, bentonite 4%, polyvinyl acetate emulsision 2.5%, CMC 0.5% and other accessories. The coasting has low cost and excellent processing properties, which is applicable to produce nodular iron casting.