The present invention relates to a quantitative self-starting and self-closing type water fertilizer slow-permeation water bag, which comprises a water storage bag, wherein the bottom portion of the water storage bag is provided with at least a slow permeation hole, the top portion of the water storage bag is provided with an automatic starting-closing valve, the automatic starting-closing valve is communicated to a water source through a water inlet pipe, and is communicated to the top portion of the water storage bag through a water outlet pipe, the bottom middle portion in the water storage bag is provided with a magnet, the automatic starting-closing valve comprises a closed soft pipe respectively communicated to the water outlet pipe and the water inlet pipe, an airbag for clogging the outlet of the water inlet pipe is arranged in the soft pipe, the bottom portion of the airbag is fixedly connected to the inner bottom of the soft pipe, the bottom portion of the airbag is provided with a gas outlet hole communicated outside the soft pipe, the outer bottom portion of the soft pipe is provided with a hinge, and the upper valve of the hinge is fixedly arranged on the bottom portion of the soft pipe. The quantitative self-starting and self-closing type water fertilizer slow-permeation water bag of the present invention has characteristics of simple structure, convenient use, and long service life.