The invention relates to the field of building decoration and provides a bathroom waterproof system which is simple in structure can convenient to construct and can effectively prevent water molecules in a bathroom from leaking outward and a construction method. The technical problems that in the prior art, the leakage proof effect of the bathroom is poor, the situation that a floor, a door sleeve and the like in a dry area mould and decay is quite prone to occurring, and the attractive degree of overall decoration is reduced are solved. The bathroom waterproof system comprises a bathroom floor base layer and a dry area floor base layer connected with the bathroom floor base layer. Ground decoration paving layers are laid on the surfaces of the bathroom floor base layer and the dry area floor base layer correspondingly. An elastic water retaining plate and the lower end of an elastic water retaining strip are arranged between the bathroom floor base layer and the corresponding ground decoration paving layer in a clamped mode, wherein the upper end of the elastic water retaining plate extends upward to the exterior of the ground decoration paving layer and connected on the bottom face of a doorsill plate in a closed mode, and the upper end of the elastic water retaining plate extends upward to the exterior of the ground decoration paving layer and connected with a cement mortar retaining strip in an airtight mode. The cement mortar retaining strip divides the corresponding floor decoration paving layer into a bathing area and a rest area.