Glacier meltwater is one of the most important components of water resources in arid region of Northwest China. When glaciers accelerate retreat, water supply capacity of glaciers will decline. Therefore, understanding of future changes in glacier runoff are crucial for water resource management in the arid region. However, the spatio-temporal differences of transition between glacier melt and glacier runoff in the past and future at subbasin scale of Northwest China remain poorly investigated. In this study, the variations of glacier runoff at multi-spatiotemporal scales are simulated by a Degree-Day glacier melt model in 25 sub-basins of Northwest China during historical (1959-2017) and future period (2018-2100). The results indicate that the glacier runoff in the study area shows an upward trend, except for a slight downward trend in the central basin of Northern Tianshan Mountains during 1959-2017. The total average annual glacier runoff is 286.88 +/- 47.32 x 108 m3 in historical period. There is a significant regional difference in the seasonality of the meltwater, with the peak value concentrated in July. The amount of glacier runoff during the ablation period in basins with large glacier areas will be higher with the increasing emission scenarios. The seasonal peak value of glacier runoff in basin with small glaciers will decrease with the increasing emission scenarios. The peak value of glacier runoff will be delayed by one month in the future compared with historical period, with most of basins occurring in August. Under different climate emission scenarios (SSP-126, SSP-245, SSP-585), the trend of glacier runoff shows significant differences at basin scales in the future. The Middle-term (2040-2069) is a period of turning transition for glacier runoff. The glacier runoff will show varying degrees of decline in the long term (2070-2100). The regional differences in distribution of glacier, precipitation and temperature lead to spatio-temporal disparities of glacier runoff in the study area. The research results can provide important scientific guidance for water resource management and response to water scarcity risks in the Northwest China.