Water tank floor drain waterproof structure and construction method thereof

The invention belongs to the field of building construction, and particularly discloses a water tank floor drain waterproof structure which comprises a first preformed hole and a second preformed hole which are vertically arranged and coaxial, an embedded pipe is embedded in the second preformed hole, the upper end of the embedded pipe is lower than the upper end of the second preformed hole, a grouting layer is arranged in the second preformed hole, and the grouting layer is arranged in the first preformed hole. The grouting layer comprises a fixing part arranged between the outer wall of the embedded pipe and the inner wall of the second preformed hole and a slope making part arranged between the upper end of the embedded pipe and the upper end of the second preformed hole, the inner wall of the slope making part is in a circular truncated cone shape, and the upper end of the slope making part is a large-diameter end; an isolation layer is fixed to the inner wall of the slope making part ...