The invention firstly provides a flake molding compound for manufacturing a manhole cover which is environment-friendly and low in cost. The middle core of the flake molding compound is composed of glass fiber cloth dipped with resin paste, the glass fiber content is 20-40 parts, the resin paste comprises the following materials: 19-23 parts of unsaturated resin, 6-8 parts of low shrinking agent, 1.4-1.6 parts of styrene, 0.5-1.5 parts of curing agent, 1.5-1.7 parts of zinc stearate, 0.01-0.03 part of benzoquinone, 0.2-0.3 part of pigment paste, and 40-50 parts of 800-1000-mesh heavy calcium carbonate. The invention further provides a method for preparing the flake molding compound. The flake molding compound provided by the invention adopts base raw material in low cost, and waste heavy calcium carbonate is adopted, so that the flake molding compound is environmentally friendly and energy-saving. The flake molding compound manufactured by using the method disclosed by the invention is high in technical content, stable in process, low in cost and strong in bearing capacity. The product disclosed by the invention is manufactured as an article which is tight in matching, wear-resistant, corrosion-resistant, light in structure, beautiful in style, light in self weight and easy to install. The social benefit and the economic benefit are obvious.