The invention discloses zero-VOC (volatile organic compound) cement-based water-proof material copolymer emulsion and a preparation method thereof. The preparation method adopts a zero-VOC copolymer emulsion component A and an inorganic powder component B, the zero-VOC copolymer emulsion component A is prepared from deionized water, alkyl acrylate, styrene, acrylic acid functional monomers, emulsifying agents, initiators, a buffer agents, polymerization inhibitors, oxidizing agents, reducing agents, sterilizing agents and defoaming agents through polymerization of pre-emulsification semi-continuous seed emulsion, and the inorganic powder component B comprises ordinary portland cement, quartz sand and water reducers. The prepared emulsion is high in solid content, low in viscosity, uniformin particle size and good in stability and has excellent rheological property and coating water absorption, the content of a residual monomer in an emulsion product is lower than 300ppm and meets national zero-VOC emulsion standards, the emulsion is environmentally friendly and free from toxicity and pollution, the compatibility of the emulsion and cement is good, and a prepared polymer cement waterproof coating is excellent in water resistance, good in low-temperature flexibility and low in water absorption.