The invention discloses an automatic-control water system for a greenhouse. The automatic-control water system comprises a comprehensive liquid tank, an ion concentration detector, a hydraulic control one-way valve, an electromagnetic ball valve, a pipeline, a water tank, a magnetic turning plate liquid level meter, an electric cable, a control console, a fertilizer supply box, an industrial pump feeding pipe, a second-stage industrial pump, a motor, a liquid fertilizer tank, a water supply tank, a pressure control system and a multifunctional nozzle, the ion concentration detector is arranged on the lower side of the comprehensive liquid tank, the hydraulic control one-way valve is mounted on the upper side of the comprehensive liquid tank, the left side of the hydraulic control one-way valve is connected with the electromagnetic ball valve which is connected with the water tank through the pipeline, and the magnetic turning plate liquid level meter is mounted on the left side of the water tank. The automatic-control water system has the advantages that time points for watering and fertilizing can be artificially set according to different flowers and plants automatically, time and manpower resources can be saved, flower and plant cultivation cost can be controlled, and economic value can be created.