An anti-freezing alkali-free liquid accelerator and a preparation method thereof are disclosed. The accelerator is mainly prepared from water-soluble aluminium salt, polyaluminium salt, alkaline earthnitrate and/or carbonate, alkaline earth fluoride salt, alcamines organic matter and water. The preparation method comprises the following steps: firstly dissolving a part of water-soluble aluminiumsalt by the use of a part of water, heating and stirring, adding polyaluminium salt and alkaline earth nitrate and/or carbonate, heating and reacting, cooling, successively adding alkaline earth fluoride salt, alcamines organic matter and the rest of water-soluble aluminium salt, adding the rest of water, and filtering. After the accelerator with the dosage of 4% is added into cement, initial setting time of cement paste is less than or equal to 4 min, and final setting time is less than or equal to 8 min; and early strength and long-term strength are both high. The accelerator of the invention has good storage stability at room temperature, low temperature and high temperature. In the case of redissolving after freezing, almost no precipitate is precipitated out, and the rapid hardening effect is not attenuated. The method of the invention has advantages of simple process, low cost and zero emission, and is suitable for industrial production.