Abstarct: Considering that underground water is an important resource for agricultural, drinking and industrial purposes, especially in arid and semi-arid areas, it is necessary to investigate and manage them. Checking water quality is usually baxsed on chemical analysis and measuring its chemical parameters. In this thesis, the quality of underground water in Gonabad plain of Razavi Khorasan province was investigated in terms of agricultural, drinking and industrial uses during the years 2007 to 2021. For this purpose, the average of 15 water parachemicals in the desired time period in 16 wells in the plain has been used. The results showed that according to the Piper diagram, the water of all the wells in the mostly alkaline and mostly strong acid categories, in the classification baxsed on cations, have sodium and potassium type, and in the classification baxsed on anions, they are mostly without dominant type. According to the FAO standard, two parameters of electrical conductivity and magnesium are more than the permissible limits. According to the irrigation indicators, they are in the inappropriate category. They have limitations for drip and rain irrigation. According to Wilcox's classification, 25.31% of the wells have medium quality water for agriculture and the rest of the wells are unsuitable. According to the results obtained from the Langelier index, in the first half of the investigated period, all the wells were in a sedimentation state, and during the second half, 43.75% of the wells had corrosive properties The results of the modified Mann-Kendall test also showed that for qualitative parameters, 125 cases of observations are increasing and 64% of them have a significant trend, 108 cases are decreasing and 73% of them have a significant trend, and seven other cases these are unchanged. For the water level in May, nine wells have a positive trend and seven wells have a negative trend, and in October 12 wells have a positive trend and four wells have a negative trend, and in both months 12 wells have a significant trend. Zoning risk of plain pollution was done by Drastic model. The results showed that 6.66%, 0.8% and 0.006% of the region were classified in the categories of high pollution, very high pollution and completely polluted areas, respectively. Validation of the Drastic model was confirmed by zoning the nitrate concentration and placing its highest amount in the polluted areas.