Plasma treatment could generate UV radiation, chemical reactions, and radicals that be able to modify the properties of a wide range of materials, including water. Water treated by plasma produces reactive nitrate-nitrogen and oxygen species that useful for the fertilization of agriculture soil and plant growth. Moreover, the water treated by plasma can be used for increasing postharvest quality of agriculture products. In this study, plasma treatment of water has been used to stimulate the germination of agricultural seed, i.e. water spinach (Ipomoea aquatica). The results demonstrate that the water spinach seeds treated by plasma-treated water not only had better germination rate and germination index, but also had a higher length index and weight. Compared with control sample, the germination rate and germination index of the plasma-treatment sample improved by 16.96% and 28.57%, respectively. Characteristics of length index also increase to 425.46. In addition, fresh weight of plasma-treatment sample was higher than the control sample by 33.3%. These results indicated that plasma-treated water might be potentially applicable for increasing water spinach plant growth.