[Background] Glacier and snowcover are the key parts of solid water resources in high alpine region, quantitative calculation of meltwater is of significance. Based on the data from the First and Second Glacier Inventory of China, the glacier area in Nam Co basin has shrunk 13.44 km~2 at a rate of 1.12 km~2/a in ten years. From the MODIS data (MOD10A2), the seasonal snow produced a large number of meltwater into Nam Co Lake. In the past forty years, the temperature increased at 0.04 ℃/a, the solid water resources (glacier) reduced by 111.73*10~8 m~3, and the lake area increased nearly 100 km~2at rate of 2.1 km~2/a. However, the correlation between temperature rising, glacier melting and lake expansion is not yet clear in Nam Co basin of the Tibetan Plateau, thus it was selected as the study area, where is covered with glaciers (141.88 km~2) and snow (20%), aiming to better understand the hydrological processes in the high alpine region under the background of global warming. [Methods] The empirical equation was presented to quantify the meltwater amount from glacier on the basis of water balance theory. Empirical values were set for the variations in the equation, including the precipitation (406.70 mm), the evaporation (100.50 mm). The glacier ablation was calculated on the basis of the glacier volume variation. The Snowmelt Runoff Model (SRM) was used to calculate the runoff amount from snow melting in the Nam Co basin, using the WinSRM Version 1.11 software. The feasibility of the SRM was discussed and analyzed. The parameters of the SRM, including the degree day factor, runoff coefficient, lapse rate of temperature, recession coefficients and air temperature, were tested in Nam Co basin using the hydrological data, meteorological data and MODIS remote sensing data (MOD10A2).[Results] The results showed that the empirical equation and the SRM model could be used for the calculation of the meltwater runoff amount from glacier and seasonal snow in Nam Co basin. The calculated annual glacier meltwater runoff was 49.15 mm/a (2.99*10~8 m~3/a), and the annual snow meltwater runoff was 8.10*10~6 m~3/a. The glacier meltwater runoff was almost 38 times that of the seasonal snow. This meant the glacier meltwater was dominant water resources in the Nam Co basin. The lake area was enlarged with the glacier shrinking when temperature increased. The increased water amount with the lake expansion was nearly 80% of the calculated runoff amount from glacier melting, far more than the calculated meltwater runoff from the seasonal snow. [Conclusions] It is deduced that the dramatic glacier melting in the Nyainqentanglha Mountains at the southeast side of Nam Co basin may be the most important drive factor for the lake expansion in the study area. However, more measurement should be conducted in the high alpine region to improve the accuracy of the calculated results by SRM. Moreover, the correlation between the glacier shrink and the lake expansion should be further investigated.