Green and clean process for preparing malonate

The invention provides a green and clean process for preparing malonate. The hydrogen chloride exhaust gas as a by-product of chlorine-relating synthesis industry or a prepared hydrogen chloride alcoholic solution is added into a reaction system, thereby not only accelerating the progress of the reaction but also reducing the side effects, improving the yield and greatly increasing the economic value added of the by-product hydrogen chloride. No three wastes are produced and just ammonium chloride as a by-product is produced in the process, so that the resources are reasonably utilized. The process is environment-friendly and has good social and economic benefits.