The Longling-Ruili fault is an important active fault in Southwestern China,striking generally northeast.The fault controls the development of the sedimentary series and magmatic action on its two sides,as well as the development of the Longling basin,Mangshi basin and the Zhefang basin along it.Due to limited Quaternary sediments and harsh natural conditions,the study of late Quaternary fault activity on the northern segment of the Longling-Ruili fault is lacking and the time of the newest faulting and the Quaternary slip rate are not clear at present.Based on the interpretation of remote images,quantitative geomorphologic deformation measurements and dating of young terrace deposits and alluvial fans,this paper obtains some new results as follows.The northern segment of the Longling-Ruili fault is a Holocene dextral strike-slip fault with some component of a normal slip.The terrace T 1 composing mainly of alluvial deposits formed during 4ka B.P.was offset by the northern segment of the Longling-Ruili fault and its left-lateral and its vertical displacements are 8m ～ 12m and 2m,respectively.The late Pleistocene alluvial fan was displaced with a left-lateral and vertical displacement of 70m and 18m,respectively.The strike-slip rate of the Longling-Ruili fault is 2.2mm/a ～ 2.5mm/a and the vertical slip rate is 0.6mm/a since the late Pleistocene epoch.The strike-slip rate of the Longling-Ruili fault is 1.8mm/a ～ 3.0mm/a and vertical slip rate is 0.5mm/a during the Holocene epoch.The proportion of horizontal to vertical displacement is about 4:1,which means that the vertical slip rate on the northern segment of the Longling-Ruili fault is about 25% of the horizontal slip rate.The left-lateral slip rate in the late Holocene is consistent with the GPS measurement.The strike slip rate is of great consistency in different time scales since the late Pleistocene epoch,indicating that the activity of the Longling-Ruili fault is of great stability. The Longling-Ruili fault is an important active fault in Southwestern China, striking generally northeast. The fault controls the development of the sedimentary series and magmatic action on its two sides, as well as the development of the Longling basin, Mangshi basin and the Zhefang the basin along it. Due to limited Quaternary sediments and harsh natural conditions, the study of late Quaternary fault activity on the northern segment of the Longling-Ruili fault is lacking and the time of the newest faulting and the Quaternary slip rate are not clear at present . Based on the interpretation of remote images, quantitative geomorphologic deformation measurements and dating of young terrace deposits and alluvial fans, this paper offers some new results as follows. The northern segment of the Longling-Ruili fault is a Holocene dextral strike-slip fault with some component of a normal slip. The terrace T 1 composing mainly of alluvial deposits formed during 4ka BPwas offset by the northern segment of t he Longling-Ruili fault and its left-lateral and its vertical displacements are 8m ~ 12m and 2m, respectively. The late Pleistocene alluvial fan was displaced with a left-lateral and vertical displacement of 70m and 18m, respectively. strike-slip rate of the Longling-Ruili fault is 2.2 mm / a ~ 2.5 mm / a and the vertical slip rate is 0.6 mm / a since the late Pleistocene epoch. strike-slip rate of the Longling-Ruili fault is 1.8 mm / a ~ 3.0 mm / a and vertical slip rate is 0.5 mm / a during the Holocene epoch. the proportion of horizontal to vertical displacement is about 4: 1, which means that the vertical slip rate on the northern segment of the Longling-Ruili fault is about 25 % of the horizontal slip rate. the left-lateral slip rate in the late Holocene is consistent with the GPS measurement. strike slip rate is of great consistency in different time scales since the late Pleistocene epoch, indicating that the activity of the Longling- Ruili fault is of stability