Lan-gan region, one of traditional agricultural production base in northern Anhui Province, East China, has rare hydrochemical reports on the formation mechanism and irrigation assessment of the Quaternary deeper confined groundwater aquifer. To better master hydrochemical characteristics, solute source, and irrigation properties, twenty-five water samples were collected from the individual digging well. Gibbs diagram, Piper diagram, ionic ratio, and multivariate statistical analysis were carried out to delineate the hydrochemical facies and water-rock interactions. Meanwhile, the USSL and Wilcox diagram, and the irrigation water quality indices were conducted to illustrate the suitability for irrigation. The results indicate that the order is Ca2+ > Na+ > Mg2+ >K+ and HCO3− > SO42− > Cl− for cations and anions, respectively. Ca-HCO3 is the main hydrochemical type. Water-rock interactions include silicate weathering, carbonate dissolution, halite dissolution and sulfate dissolution. Based on EC value, the majority of the samples are permissible for irrigation, whereas only 12% of the samples were found good for irrigation. The RSC, SAR, and %Na, combined with Wilcox diagram and USSL diagram, demonstrate that the groundwater samples are permissible for irrigation purpose.