Based on the analysis of the geological and hydrogeological conditions of the Weihe River Plain, by using the monitoring data of groundwater quality during recent two decades, this paper discussed the changing law of groundwater quality over time, and conducted a comprehensive evaluation of groundwater quality, analyzing the main influencing factors. The results show that the quality of groundwater in the Weihe River Plain is generally good. The comprehensive evaluation of water quality in the western part of the Qinling Mountains and the upper part of the Weihe River is excellent . The comprehensive evaluation of water quality in Loess Plateau of Weibei and lubotan in the downstream of the Weihe River is poor or very poor. The excessive materials in different regions are different, the main excessive items are summarized as total hardness, sulfate, chloride, nitrogen, fluoride, etc; The concentration of groundwater in the centralized mining area of major cities is greatly affected by the amount of pollutants, and the depth of water level is positively correlated with the content of sulfate, nitrate and total hardness. The main influencing factors of groundwater quality change are artificial mining, natural background value, local pollution, precipitation and so on. The results of the study are of great significance to the protection and rational exploitation of groundwater quality in the Weihe River Plain.Based on the analysis of the geological and hydrogeological conditions of the Weihe River Plain, by using the monitoring data of groundwater quality during recent two decades, this paper discussed the changing law of groundwater quality over time, and conducted a comprehensive evaluation of groundwater quality, analyzing the main influencing factors. The results show that the quality of groundwater in the Weihe River Plain is generally good. The comprehensive evaluation of water quality in the western part of the Qinling Mountains and the upper part of the Weihe River is excellent . The comprehensive evaluation of water quality in Loess Plateau of Weibei and lubotan in the downstream of the Weihe River is poor or very poor. The excessive materials in different regions are different, the main excessive items are summarized as total hardness, sulfate, chloride, nitrogen, fluoride, etc; The concentration of groundwater in the centralized mining area of major cities is greatly affected by the amount of pollutants, and the depth of water level is positively correlated with the content of sulfate, nitrate and total hardness. The main influencing factors of groundwater quality change are artificial mining, natural background value, local pollution, precipitation and so on. The results of the study are of great significance to the protection and rational exploitation of groundwater quality in the Weihe River Plain.