Abstract: When the NFT hydroponics be used, it is necessary to set up an ideal installation and watering system. The key to the settlement of the project lies in the automatic intermittent circular watering system.Authors used the automatic intermittent circular watering system day and night controlled by a self-made electronic program controller. The results of this experiment show that the growth rate of different stages of tomato influenced by the watering systems is that: the day and night intermittent circular watering system is better than the day time continuous circular watering system or once a day watering system.The fruiting stage of day and night intermittent circular watering system was half a month earlier than above other two systems.The height of the plant, number of leaves, root system, resistance of stomata and leaf blade transpiration with the day and night intermittent circular watering system were all better than other two watering systems. The yield of the single plant of tomato cultured uuder above three watering systems is arranged as follows: day and night intermittent circular watering system is the highest, day time continuous watering system is the medium, and once a day watering system the lowest. The highest yield is ten times as high as the lowest oneIt is due to that the day and night intermittent circular watering system solves the contradictions of exchange of the water-gas phases within the solution. A water film is always existed at the top of the solution bed, which will make the plant roots never out of solution. All these promote the plant growth.Surely the pH value and EC value of the cultural solution are also very important for the hydroponic culture. It will be preaented in another paper.