Abstract: The lower Yuka River is in Mahai Basin near the north border of Qaidam Basin, and groundwater is one of the key water sources there. We calculated water budget of the groundwater system from 2000 to 2013 based on basic the characteristics of hydrogeology, and coupled with the meteorological and hydrological data obtained from relevant literature and field investigation and test. The results show that river leakage recharge is the main source of groundwater system in the valley, accounting for 77.8%of the total replenishment; and phreatic water evaporation is the main discharge form, accounting for 85.6% of the total discharge. The total annual average replenishment to groundwater in the valley was about 10 260.5×10⁴ m³/a, and the total annual average discharge of groundwater was about 10 896.6×10⁴ m³/a. The groundwater balance difference was - 636.1×10⁴ m³/a, and the groundwater level declined at a speed of 59 mm/a. The results are significant for groundwater resources calculation, groundwater environment protection and ecological environment protection for the basin.