Abstract: Based on the observed streamflow of 19 key hydrological control stations in the six larger basins in China for the past 50 years,this study employed the Mann-Kendall test to detect trends of annual runoff. It was found that annual runoff in the six larger basins has generally decreased during the periods,with signicant decreases detected in the northern China. Especially in Haihe river,Yellow river,Liaohe river and Songhuajiang river,there are remarkable decreasing trends.