In the past 50 years,climate change and increasingly extensive human activities have greatly altered the runoff in Beiniuchuan River Basin.Based on the climate and hydrological data in Xinmiao station during 1966-2010,runoff variation characteristics and the influencing factors were studied.Mann-Kendall trend analysis, statistic analysis,R/S analysis,and double mass curve were used comprehensively in the study.The results indicated that the multi-year change of runoff had a decreased tendency in all,and this trend was the most evident since the end of the twentieth century.The runoff affected by rainfall and human activities appeared three change periods in which the turning years were 1979 and 1997 respectively.The effect of precipitation on runoff decreased,the influence rate reduced from 67.97% in 1979-1996 to 13.53% in 1997-2010.The influence of human activities on runoff gradually increased,the influence rate increased from 32.03% in 1979-1996 to 86.46% in 1997-2010.Since 1997 the human activities have moved into the primary factor.The Hurst index was 0.8735 for the Xinmiao station which indicates that the decreasing trends in Beiniuchuan River runoff would continue in the future.