¹³⁷Cs and ²¹⁰Pb techniques are used to date a sediment core (MG4-2) retrieved from Maigang Reservoir in Ziyun County,Southwest Guizhou and infer its sedimentation rates. Three distinctive ¹³⁷Cs peaks are identified in this core,which are ascribed to the abundant fallouts occurring in 1964,1975,and1986. The ²¹⁰Pb ages calculated with CRS model are generally coincident to the ages inferred with ¹³⁷Cs activities. However,there are also some discrepancies in the dates derived from the two methods. In particular,the age calculated with ²¹⁰Pb for the depth with an age of 1964 inferred with ¹³⁷Cs activities is remarkably different from the ¹³⁷Cs age. Although the sedimentation rates derived with the two methods are different,both of them indicate a quite similar trend of changes in accumulation in the reservoir during the last decades. Sedimentation was rather slow in the earlier stage,then was fast in the middle stage,and finally slowed down again in the later stage. Such variations in sedimentation rate in MG4-2 may be due to the human being activities in the catchment of Maigang Reservoir. Simultaneous uses of ¹³⁷Cs and ²¹⁰Pb methods may allow cross-checks of the results derived with the two methods and thus lead more reliable and accurate chronology and sedimentation rate.