Abstract. The Otindag Desert in the middle-latitude desert zone of northern Hemisphere (NH) is essential to livestock-economy and ecoenvironment of northern China. Many areas in this zone are unexpectedly rich with groundwater resources although they have been under arid or hyper-arid climate for a long time. Widespread fresh groundwater deep to 60 m was found at the eastern part of the Otindag Desert. The occurrence of this massive fresh groundwater raises doubts on the long-lasting hypothesis in academic circles that regional atmospheric precipitation or palaeowater, namely the direct recharge, is the source of water in the middle-latitude desert aquifers of northern China. Understanding of the recharge of this fresh groundwater is important in evaluating the feasibility of groundwater exploitation and utilization. In this study we conducted hydrogeochemical and isotopical analyses to assess possible origin and recharge of these groundwaters. The analytical results indicate that the fresh groundwater is neither originated from regional atmospheric precipitation derived from the Asian Summer Monsoon system, nor from palaeowater that formed during the last glacial period. These findings suggest that the groundwater in this desert is possible to originate from remote mountain areas via the faults of the Solonker Suture zone, including the Daxing’Anlin and Yinshan Mountains. In addition, it is concluded that the hygeodrological linkage between desert aquifers and mountain systems through the suture zone is crucial to the hydrological functioning of the Otindag aquifer. This suggests that the modern indirect recharge mechanism, instead of the direct recharge and the palaeo-water recharge, is the most significant for groundwaterrecharge in the Otindag Desert. This study provides a new perspective into the origin and evolution of groundwater resources in the middle-latitude desert zone of HA.