In order to solve the problems of the small lateral diffusion range of water in the soil and the leaching of nitrate nitrogen,the water regulator DY-ET100 was used as the test material,with the water and thirst as a control. The effects of nitrogen addition on the diffusion of water in different types of soil and nitrate nitrogen leaching and tomato yield and quality were studied. The results showed that the addition of moisture regulator DY-ET100 to sand-doped and non-sand-doped clay significantly increased the VC contents of tomato fruits by 12.50% and 20.51%,respectively. The treatment with DY-ET100 resulted in the more evenly distribution of water in soil of the 0~30 cm distance from the dripper. The water diffusion radius during drip irrigation were 22.53% and 12.33% higher than that of clear water and thirst. The accumulation of nitrate nitrogen in sand-doped and non-sand-doped clay was increased by 41.21% and 18.83% respectively compared with the water treatment. At the same time,the leaching loss of nitrate nitrogen was reduced by 7.53% and 8.07% respectively in sand-doped and un-sand-doped clays compared with the water treatment. This study provided data support for the promotion of water regulators.