This paper is the result of hydrogeological survey engineering. Objective The Beiluo River Basin is an important secondary tributary of the Yellow River. Research on groundwater quality in typical tributary basin of theYellow River is of significant for ecological protection and high-quality development. To ensure local drinking water safety, we systematically identified status of groundwater quality and delineated inferior groundwater region in the Beiluo River Basin. Methods Besides, based on analysis of D-¹⁸O isotope in groundwater, characteristics and evolution mechanism of groundwater hydrochemistry were studied and effects of hydrogeological condition and anthropogenic activities on groundwater hydrochemistry were revealed. Results Groundwater hydrochemical composition was jointly affected by rock weathering and evaporation concentration, part of which was influenced by anthropogenic activities. D-¹⁸O isotope composition suggested that evaporation concentration is the major influence factor of groundwater hydrogeochemistry. Conclusions Leaching of soluble minerals such as gypsum halite in clasolite and evaporation concentration of pore water in Cenozoic faulted basin in the downstream caused salt accumulation and high TDS in groundwater in the upstream and downstream, respectively. Hydrochemical composition of groundwater in Ordovician karst aquifer and Cenozoic faulted basin aquifer was mainly controlled by evaporites and anthropogenic activities. While hydrochemical composition in Cretaceous aquifer and Carboniferous-Jurassic aquifer was mainly controlled by rock weathering (especially silicate rocks and evaporite) and less affected by anthropogenic activities. Moreover, groundwater in the upstream and downstream was significantly affected by industrial and mining activities. While groundwater in the midstream is of good quality due to less influence of industrial/mining activities, agricultural activities and domestic wastewater.