The Tibetan Plateau （TP） and its adjacent areas are located in the intersection zone of the East Asian and Indian summer monsoons， and the westerly circulation. Characterizing and interpreting the spatial distribution of precipitation and the climatic boundary across the TP are important for understanding the dynamics of atmospheric circulation in this tectonically and climatically sensitive region. Rock magnetic investigations of surface soils have been successfully used to identify the spatial pattern of climatic gradients in the Eurasian continent and North Africa， especially where meteorological stations are sparse. Here we conducted detailed investigations of the magnetic properties of a large set of surface soil samples， combined with the analysis of some 70 years meteorological dataset to characterize the spatial distribution of precipitation in the TP and its adjacent areas. The results demonstrate that pedogenic intensity decreases significantly as moist air flows across the TP towards the interior， which directly demonstrates the effect of the precipitation gradient on pedogenesis. This finding confirms that rock magnetic investigations of surface soils in the TP and its adjacent areas are an effective method for characterizing the precipitation boundary in this vast area. Based on a synthesis of the rock magnetic and meteorological data， we have clearly defined the presence of two distinct boundaries in pedogenic intensity in the northwestern and southeastern TP， i.e.， the Pamir Plateau-the Tianshan Mountains and the Qilian Mountains-the Hengduan Mountains， which correspond to the critical precipitation boundary between sub-humid to semi-arid and arid regions in the TP and its adjacent areas. Moreover， a comparison of several last glacial-interglacial loess sequences in the northeastern TP demonstrates that during the warm and humid interglacial periods， a steepened rainfall gradient occurred， which can be attributed to the ice sheet recession and increasing temperature and moisture cycles. These findings will provide foundation and boundary conditions for future paleoclimatic reconstructions and climate simulations in the Eurasian continent.