Hydrogeochemistry has long been the research focus in the field of hydrogeology. But temporal and spatial variation characteristics of groundwater chemical components are affected by many factors. In this paper, karst groundwater sampling sites were arranged in Baotu spring hydrogeological unit to collect karst groundwater samples in dry and rainy season in order to research spatiotemporal difference of karst groundwater hydrochemical characteristics by mathematical statistics, correlation analysis, Piper diagram, Gibbs diagram and ion proportional coefficient method. The results show that the dominant cation in groundwater is Ca and the dominant anion is HCO3. The variation coefficients of other ions (greater than 0.5) in rainy season are generally higher than that of dry season expect HCO3, which indicates increasing of spatial difference during rainy season. Groundwater types are mainly HCO3·SO4- Ca coexisting with many types. Ratios of Ca, Mg and HCO3 contents are less than one during dry and rainy season and are stable than other ions, presenting an integrated feature. Na and K contents fluctuate greatly during dry and rainy season with their ratio more than one. Cl, SO4 and NO3 contents have a characteristic that the ratio fluctuates greatly in dry and rainy season, presenting regional features. These characteristics of spatiotemporal difference indicates that human activities have greatly changed the distribution pattern of groundwater chemical field in the study area.