The invention discloses a water-based surface treatment agent for calendered PVC (polyvinyl chloride) leather, which is mainly prepared from water-based PU (polyurethane) resin, deionized water, a water-based leveling agent, a water-based defoamer and a water-based thickener by weight parts. Matting power and a water-based anti-adhesive can be also added to prepare the water-based surface treatment agent for the calendered PVC leather. The tests prove that the leveling property and the drying property of the water-based surface treatment agent for the calendered PVC leather can meet the requirement, is comparable with the traditional solvent product in surface treatment effect such as adhesive force, gloss and haze and is superior to the traditional solvent product in scratch resistance, hand touch sense fullness and texture finesses. The formula of the water-based surface treatment agent can be applied to the prior calendered PVC leather production line without changing the prior calendered PVC leather production equipment and increasing the calendered PVC leather product production cost. The water-based surface treatment agent for the calendered PVC leather is safe and environmental friendly, is easy to prepare, has low cost and can realize the industrial large-scale production easily.