Based on the measured data of runoff and sediment in monthly time scale from 1970 to 2012 of Yuanmou arid valley in the lower reaches of the Jinsha River, the linear trend estimate, mean cumulative curve, Yamamot test and Morlet wavelet analysis method were employed to study the water and sediment evolution rule. The results showed that: more than 85% of water and sediment transportation in Yuanmou arid valley are during the annual monsoon period, since the 1970s, the water and sediment transportation amount showed a slightly decreasing trend, water production accounted for the proportion of the whole basin showed a decline trend while the sediment yield ratio presented an increasing trend. The runoff and sediment process has two abrupt points since 1960's, the abrupt point of runoff was in 1992 and 1994 for the sediment, while the runoff and sediment both have an obvious abrupt point in 2002. The periodic variation of annual runoff and sediment is the most significant in the 28 year time scales, which is the first main cycle, and there were one complete wet, sandy center year and one complete center year of less water and sand. In addition, the periodic variation in 13 years time scale is also prominent too. Compared to the runoff, the sediment yield in Yuanmou arid valley has an increasing trend since 1992 but presented a decreasing trend since 2003.