The invention provides an environmental, economical and efficient CO2 hydrate formation promoter. The main additive and the auxiliary additive are dissolved in the water to form a mixed solution; the contents of the main additive and the auxiliary additive are separately 0.10-0.35% and 0.014-0.055% of the total amount of the mixed solution by molar percent and the allowance is water; the main additive is composed of one or more quaternary ammonium compounds with the general formula (I) and the auxiliary additive is composed of one or more quaternary ammonium compounds with the general formula (II). The CO2 hydrate formation promoter of the invention has the advantages that the dissolution of CO2 in aqueous solution can be effectively improved; the formation pressure of hydrate can be significantly reduced; the hydrate formation speed can be improved; the concentration of CO2 in hydrate phase decomposition gas can be increased; the promoter can be recycled; the process of separation has no pollution and the promoter is economic, environmental friendly, efficient and the like, thus being applicable to CO2 separation with low cost of various mixed gases such as flue gas, IGCC synthesis gas, natural gas and the like.