The slip rate of Altyn Tagh Fault (ATF) was studied near the Aksay segment (39°24.572´N, 94°16.012´E), China, based on dating the terraces of a river passing through the ATF. Two river terrace risers were offset by the ATF and the fault displacements were recorded. Average slip rate of the Aksay segment of the ATF was estimated using the offset of terrace risers divided by the corresponding ages. The ages of the terraces were determined by optical dating of the loess deposited on the river terrace. Our results demonstrated that: (1) The optically stimulated luminescence (OSL) ages of loess can be used to constrain the terrace ages in the study area. (2) The average slip rate of the Aksay segment of the ATF in the last 6 ka is about 12±1 mm/yr, given specific geomorphic assumptions discussed in the text. (3) In this situation, rather than the lower terrace age, the upper terrace age should be used in slip rate calculation as it is closer to the riser offset duration.