We take the representative farmland-type and woodland-type depression small watersheds in the Qingmuguan karst valley region as the research object, and start from the depression sediments, the depth distribution characteristics of ¹³⁷Cs specific activity, HCHs, organic matter, clay content, and bulk density of the sediments in each depression profiles were studied. ¹³⁷Cs tracer method and HCHs were applied to sediment dating, and the evolution characteristics of soil erosion in karst depression small watershed in the past 60 years was traced, and its driving factors were discussed. The results show that:(1) Only a few sediment profiles had detected ¹³⁷Cs and HCHs in the farmland depressions of Fort Yard. The depth distribution of ¹³⁷Cs and HCHs could not be used for sediment dating, which reflected that the developed sinkhole had a great impact on the sediment profile. (2) The sand production modulus of the Longdongcao farmland depression in 1963-1983 and 1984-2019 were 231.78 and 82.04 t/(km²·a), respectively, while those values in Laodong village woodland depression small watershed were 68.79 and 39.46 t/(km²·a), respectively, indicating that the ecological environment of the basin has been significantly improved. Compared with 1963-1983, there was no significant change in the average annual precipitation in the region from 1984 to 2019. The sand yield modulus of the two small watersheds both decreased significantly, indicating that the sand yield intensity of the basin in the past 60 years was mainly controlled by land use, water and soil conservation measures and other human activities. (3) The peak value of ¹³⁷Cs and HCHs of profile, surface sediment ¹³⁷Cs, HCHs values and watershed sand yield modulus in different periods of Longdongcao depression were significantly greater than those of the Laodong village depression. It was mainly caused by the difference in sand production intensity under the influence of human activities, which conducted in the cultivated land and woodland type small watershed of the two depressions. In addition, the combined tracer method of ¹³⁷Cs and HCHs could be used to assess the temporal changes of sediment yield in the southwestern karst basin.