The invention discloses a construction method for pouring waterborne concrete through an assembled distributing rod of an idle square barge and belongs to the technical field of building construction. The construction method comprises step (1) of assembling the distributing rod and step (2) of pouring the waterborne concrete through the distributing rod. According to the construction method, the construction process based on the distributing rod, a ground pump and the square barge is adopted, the waterborne concrete pouring effect is significant, the construction efficiency is improved, the construction speed is accelerated, the concrete quality control is ensured, particularly during waterborne cast-in-place pile concrete pouring, the pouring effect is more outstanding, the pile foundation concrete pouring quality is ensured, the site safety is ensured, and the impact of a ship on a construction platform is limitedly reduced.