The application relates to an automatic drain system for bottom plate construction or reinforcement construction of a stilling pool and a manufacturing and use method thereof in water conservancy project. The automatic drain system comprises a water pump and collector pipes; the water pump is provided with a PLC (Programmable Logic Controller) control panel, a water inlet pipe and a water outlet pipe, the water inlet pipe is provided with a plurality of branch water inlet pipes, the branch water inlet pipes are connected with water pumping pipes respectively, respective water pumping pipes are connected onto the corresponding collector pipes, the collector pipe are arranged at water seepage positions, the upper opening parts of the collector pipes are provided with sensors, and a floating body rises along with water level to approach to each sensor and send a water pumping starting command to the water pump; the water outlet pipe is provided with a detector, and when detecting that water yielding in the water outlet pipe is stopped or water level is lower than a set value, the detector sends a water pump closing signal. By adopting the solution in the invention for bottom plate construction or reinforcement maintenance of the stilling pool, construction cost is saved, construction time is saved, emptying of upstream stored water is not required and loss of water resource is reduced.