Understanding the sediment delivery ratio (SDR) is important in controlling sediments for the sustainable development of natural resources and in the design of the construction such as dams and reservoirs. The purpose of this investigation is to determine the SDR by the 137 Cs tracing method in a small watershed in the Sichuan Hilly Basin of China. In the study watershed, different land plots are divided according to the land use type, and 97 sampling sites were selected from these plots. The results show that the average net soil loss rates from the forest land and sloping cultivated land are 1759 and 4468t/km 2 a, respectively. No 137 Cs was detectable on the bare rock surfaces and previous work showed that the erosion rate from the bare rock area was 14,260t/km 2 a. In the depositional zone, the sedimentation rates in the Caoto (a kind of cultivated land located at the foot of hills) and paddy field are 3113 and 3562t/km 2 a, respectively. Combining the area of each land use in the small watershed, the SDR of 0.40 is obtained in the past four decades. The 137 Cs technique was shown to provide an effective and rapid means of estimating the SDR within the small watershed.