A pet water feeder outlet pipe with a water stop structure which includes an outlet pipe located at the bottom of a pet water feeder, a guiding torus and a concave ring groove. The guiding torus and concave ring groove are located in the inner wall of the outlet pipe respectively, and the concave ring groove is located between the outlet pipe orifice and the guiding torus. A ball is movably held in the outlet pipe, and partially projects from the orifice of the outlet pipe. A water stop washer is located in the concave ring groove, and the inner edge projects from the concave ring groove inwards. An inner ring flange is provided on the inner edge of the water stop washer, and the ball optionally clings to the water stop washer and the inner ring flange, so as to seal the outlet pipe for water stoppage.
