The black locust (Robinia pseudoacacia Linn.) is a typical soil and water conservation plant widely distributed in Lvergou watershed of loess hilly area on the Loess Plateau. In this study, the radial growth of black locust and its response to climatic factors were investigated, and the applicability of estimating annual runoff and sediment transport in the watershed by using the ring width of black locust was evaluated. The results indicated that:(1) the radial growth of black locust plantation in Lvergou watershed showed an obvious downward trend with forest age. Black locust was in a rapid radial growth period ((4.17±0.74) mm/a) in the young forest stages (1-10a) and then the radial growth gradually decreased, and the average growth rate of middle, mature and over-mature forest stages (11-40 a) was (2.31±0.41) mm/a, which decreased by 44.60% compared with the previous period. Basal area increment (BAI) of black locust increased at an average rate of (5.46±2.13) cm²/a from 1-10 a, then kept an upward trend from 11-40 a, but its annual growth fluctuated greatly, with an average growth rate of (10.80±1.95) cm²/a. (2) The radial growth of black locust was negatively correlated with temperature, and positively correlated with precipitation, relative humidity and Palmer Drought Index (PDSI). The radial growth of black locust was negatively correlated with the mean temperature and maximum temperature in August, September (P<0.05) of previous year, July (P<0.01) of current year, and positively correlated with the minimum temperature in May (P<0.05) of current year. It was significantly positively correlated with the precipitation in June and July of current year and the relative humidity in August of previous year and July of current year (P<0.05), and significantly negatively correlated with the relative humidity in March of current year (P<0.05). The growth of black locust was positively correlated with PDSI in June of previous year, October of previous year to January of current year and March to August of current year (P<0.05), which means that drought stress inhibited the growth of black locust significantly. (3) From 1978 to 2017, the annual runoff and sediment transport in the Lvergou watershed showed a decreasing trend, and the inter-annual fluctuation was large, with an obvious period of wet and dry. The runoff and sediment transport were significantly affected by precipitation, and the runoff and sediment transport were positively correlated (P<0.001). (4) Our results indicated that using black locust tree rings to estimate the annual runoff and sediment transport in Lvergou watershed was effective (P<0.02), and the method was feasible. In comparison, the estimation of runoff and sediment transport under natural conditions was better than that of under the influence of human activities. Our research findings demonstrate that tree ring analysis can be employed as a valuable tool for estimating hydrological data in regions where such observations are limited or unavailable.