[Background]Most of the existing researches focus on large-scale watersheds and humid regions,but there are few studies on runoff changes in arid grassland basins,especially the systematic study of runoff variation laws at different time scales. The study on the characteristics of runoff changes in the basin of the grassland area has important application value and guiding significance for the reasonable development and utilization of local water resources. [Methods] Located in the southeastern part of Inner Mongolia,the Xilin River Basin is a temperate semi-arid continental monsoon climate. It has the characteristics of less precipitation,more evaporation,and larger temperature difference. The measured flow data from 1968 - 2015 are from Xilinhot Hydrological Station. Mann-Kendall trend test method was used to analyze the decennary,annual,seasonal,and inter-annual trends of runoff depth from 1968 - 2015 in the Xilin River Basin. The temporal and spatial variations of river runoff at home and abroad were compared to illustrate the differences between grassland-type rivers and large rivers. [Results]1) The average runoff in the 1990s was the largest with large fluctuation,and that in the rest of years showed a decreasing trend. 2) The annual runoff during 1968 - 2015 demonstrated a significant decline over time. 3) The seasonal runoff showed a significant downward trend. Among them,the decline rate in the spring and summer was insignificant,while that in the autumn was significant,and the runoff in the autumn was almost zero after 2005.4) The inter-annual runoff depth distribution was uneven with bimodal,which peaked in April and August respectively. 5) According to the Mann-Kendall mutation test,a abrupt change of runoff depth in Xilin River Basin occurred in 1984 and 2000. The period from 1968 - 1984 was defined as the base period,and the period from 1985 - 2000 and 2001 - 2015 was defined as an abrupt change period. Runoff increased during 1985 - 2000 by 22.84% while compared with the baseline period. The runoff during 2001 - 2015 showed a significant decrease,by 42.89% compared with the baseline period. [Conclusions]The main factor in the reduction of runoff in the Xilin River Basin is human activities,in which socio-economic factors such as population increases,industry and animal husbandry development affect the runoff of the Xilin River Basin. This study provides scientific basis for the optimal allocation of water resources in the Xilin River Basin. The series of ecological protection measures may reduce the impact of human activities on watershed runoff.