The invention relates to a waterproof material for a cement concrete bridge floor and a preparation method of the waterproof material. The waterproof material is obtained by the following steps of: generating amino methyl acid ester by using isocyanate and compound polyalcohol, then adding ordinary heavy-traffic paving asphalt, and compounding and modifying by a tertiary amine catalyst, a compound antifoaming agent and ethyl acetate. The waterproof material can be firmly bonded with the cement concrete bridge floor, the resistance to high temperature and low temperature is good, the waterproof material can undergo comprehensive function requirements of temperature transforming and long-term loading, the destruction of the bridge structure caused by water seepage is alleviated, the service life of the road bridge is prolonged, the construction operation is safe and simple, the construction speed is high, the film forming time is short, the requirement on bridge floor construction is not high, and the construction can be carried out fast. The preparation method of the waterproof material is simple and easy to operate, the isocyanate, the compound polyalcohol and the ethyl acetate in a dehydrated state are not decomposed or oxidized in vacuum, so that the stability of each component is guaranteed and the prepared waterproof material has high solid content and good material performance.