Abstract: Suspended sediment is an important carrier of river biogenic material transportation. Clarifying the temporal change characteristics of suspended sediment transport rates in rivers can provide basic information for understanding river ecological rhythms. This paper studies the monthly monitoring data of suspended sediment transport rates and discharge from 1956 to 2000 at the Nugesha,Yangcun,and Nuxia hydrological monitoring stations in the middle reaches of the Yarlung Zangbo River. The missing periods are interpolated by using an established water-sediment relationship. Morlet wavelet transforms,concentration degree and concentration period analysis methods are then used to explore the characteristics of sediment transport changes under different time scales in the watershed. The results show that the suspended sediment transport rates series from the three stations all assumed periodic changes in multiple time scales,maintaining a highly spatial consistency with their four major cycles being 19 years,26 years,10 years,and 6 years,respectively. There is a certain response between the short-period changes of sediment transport rates and the periodic changes of solar activity and climate events. The maximum sediment transport rate of the three stations mainly occurs in July and August,and the concentration degrees are 0.83,0.77,0.74,respectively. Affected by differences of local meteorological condition,the uneven distribution of sediment transport rates during the year gradually decrease along the river. Moreover,the sediment transport rate showed an abrupt change in 1964 when an increasing trend changed into a decreasing trend.Precipitation and human activity are believed to contribute to this reduction,with the contribution rate from precipitation in the three stations were 38.62%,41.04%,and-38.15%,respectively,and the contribution rate from human activity were 61.38%,58.96%,and 138.15%,respectively. This study preliminarily clarifies the multi-time-scale variation characteristics and main control factors of the suspended sediments transport process in the middle reaches of the Yarlung Zanbo River when there are no obvious disturbs from large-scale water conservancy projects,which can provide a natural state reference system for ecological protection in the Yarlung Zangbo River.