Abstract: In recent decades, precipitation on the Tibetan Plateau（TP）increased in the north and decreased in the south, leading to greater complexity and uncertainty of the water resources system. To improve our knowledge about those changes, on the basis of an existing method for calculating precipitation recycle rate, a new method for tracking water vapor transport and estimating relative contribution rates of different water vapor sources is proposed to quantify the contribution of different water vapor sources to the precipitation and its changes in the TP. The study shows that the southwestern source area controlled by the Indian monsoon, the western source area by the westerly, the local source area by recycled water vapor, and the southeastern source area by the East Asian monsoon contributed 38.5%, 31.6%, 24.6%, and 0.2%, respectively, of the water vapor to the precipitation in the TP during 1980—2020. The southwestern source region dominated the increase in precipitation in the southwestern TP, contributing 42.9% of the water vapor to the overall increase in precipitation in the TP. Meanwhile, the local recycle source area is the main water vapor contributor to the precipitation increment in the central and northern part of the TP, contributing 36.2% of the water vapor to the overall increase in precipitation in the TP. The western source area contributed 10.6% of the water vapor to the overall increase in precipitation on the TP, with increasing contribution to the northwestern part of the TP and decreasing contribution to the eastern and southern parts.