The kinematics and evolution of multiple fault branches derived from on base fault is one crucial problem in understanding topography building and crustal deformation along active orogens.Standing along the NE margin of the Tibetan Plateau,the Qilian Shan(Shan means mountain in Chinese)supply an ideal region to probe this problem.In this study,we mapped and surveyed several levels of fluvial terraces along the Xiying River,which transects three branches of the NQF system in the eastern Qilian Shan.Using deformation of terrace surfaces and terrace ages(OSL method),we determined vertical fault slip rates of 0.22 ±0.07 mm/a since~53 ka for the H-T fault,and of 0.60 ±1.2 mm/a from~121 ka to~76 ka,0.67 ±0.18 mm/a from~76 ka to~56 ka,and 0.09 ±0.01 mm/a from~56 ka to present for the KNQ fault.When we compare the river incision rates on the hanging wall with the vertical slip rates of the faults,we find that river incision rates are higher than vertical fault slip rates.Then based on our observation and previous studies,we proposed a simple geometry and kinematic model to interpret the river incision rate and fault slip activities.