Cluster analysis and factor analysis were used to identify the chemical characteristics and influencing factors of karst groundwater samples collected from northern Bijie City in October, 2013. The results indicated that, due to the influence of geographical factors, water-rock interaction, soil and natural processes and human activity, the karst groundwater exhibited spatial variability, and there was significant variation in the chemical composition. Moreover, the essential hydrochemical characteristics(82%) and geochemical processes of groundwater can be explained by geographical factors, water-rock interaction, soil and natural processes and human activity. Among them, the water-rock interaction and human activity were the crucial influence factors. The HCO₃^-, SO₄^2-, Ca²⁺ and Mg²⁺ in groundwater mainly came from the dissolution of carbonate rocks, and the mining activity was another source. In addition, the factors of soil and water-rock interactions controlled the concentrations of Mg²⁺, HCO₃^- and CO₂. The concentrations of Cl^-, K⁺, Na⁺ and NO₃^- in groundwater were mainly influenced by human activities, including runoff of fertilizer and manure, pesticide application and discharge of sewage. The results are instructive for understanding the hydrochemical characteristics of karst groundwater in southwest China, and hence can improve local government's management and utilization of groundwater.