The daytime discharge was less than the night-time discharge in the Rongbuk Glacier catchment in June 2005, because of the large glacierized area and many glacier-lakes immediately beneath the glacier, which indicated that the glacier had pronounced water storage function. Between the maximum discharge and the maximum temperature there was a time-lag of 9~14 hours. As the glacier ablation went on, the glacier drainage system became perfect and the time-lag decreased. An exponential formula was developed between daily mean discharge in the gauging site and daily mean temperature in Tingri County for the clear weather days. The formula was validated by the daily mean temperature and daily mean discharge in 1959, when a scientific expedition was carried out. Calculated discharge and modeled discharge by the formula during the rainy days were compared and a discharge difference was found. It is believed that the difference was induced by precipitation, accounting for 19.2% of the total discharge. The discharge induced by glacier ablation accounted for 80.8% of the total discharge.