This study was researched on the trends of water quality using lysimeters and cylinder pot to examine utilization of the paddy fields for purifying water quality. Two type of experiments purifying water quality have been executed, the one was the model of using lysimeters supposing about the histories of land use conditions, the frequencies of circulating irrigation water and aeration methods. Another was the model of using cylinder pot consisted four soil layers simulated the part of the paddy fields. The comparison with the histories of land use conditions, the effect of purifying water quality with the model of the general paddy field was better than the restored paddy field. Comparing with the frequencies of circulating water, the effect of purifying water was verified every models, but there weren't any feature with the difference of the frequency. In the case of the aeration method model, nutrient rich salts in the irrigation water haven't changed very much. According to the experiment about cylinder pot, the concentrations of the nutrient rich salts in the soil water have decreased greatly at the layer of plowsole. As a result of these experiments, it was important for removal nutrient rich salts with paddy fields to be formed impermeable layer of plowsole, and more effective to percolate as slowly as possible.