The present invention relates to a method for growing a plant on the water by using an air cap. A conventional method for growing a plant on a reservoir or on the water requires high expenses, and thus is economically unbeneficial, as it is necessary to make a raft, place soil on the raft, and grow a plant on the soil. The method for growing a plant on the water by using an air cap, according to the present invention, is configured to: make holes at predetermined intervals on a packing air cap instead of the raft place seeds or plant seedlings in the holes place the air cap on the water for plant roots to overgrow from the air cap on the water such as a reservoir or the like into the water and allow the plants to grow. More specifically, the method of the present invention comprises the following steps: fixating an edge pipe (1) around the edge of the air cap to protect a plant from wind making holes (3) at predetermined intervals on the air cap (2) and placing seeds or planting seedlings in the holes and placing the same on the water (1) for the plants to float on the water such as a reservoir or the like, and for plant roots to overgrow from the bottom surface of the air cap (2) into the reservoir, and thus making the plant grow. Javan Waterdropwort or the like does not require soil to grow, and thus can be planted as it is into the air cap holes (3) however, a lotus or the like requires soil for roots to be placed. Thus, the method of the present invention: makes an exclusive plant cultivation pot places a fabric or the like inside the plant cultivation pot to prevent the soil from being washed away and loads soil and puts the plant into the air cap holes (3) to grow. Therefore, the present invention enables plants which require soil and plants which do not require soil to grow on the water. In addition, the method for growing a plant on the water by using the air cap according to the present invention: is configured to connect a fixing string to the edge pipe (1
