Biochar addition can change the physiochemical properties of soil, thus likely influencing soil's resistance to rill flow (reflected by rill erodibility (Kr, s m(- 1)) and critical shear stress (tic, Pa). However, the persistent time effects of biochar on Kr and tic have remained unexplored. This study aimed to assess the impact of biochar composed of apple branches on Kr and tic, and to investigate the relationships between Kr, tic and soil properties. The undisturbed soil core samples to a depth of 5 cm were collected from field plots that had received biochar at rates of 0, 1, 2.5, 4, 5.5, and 7% (w/w) after 1, 2, and 3 years, respectively. The Kr and tic of these samples were evaluated through a flume experiment, with scouring soil samples under three flow discharges (e.g., 0.00025, 0.00045, and 0.00065 m(- 3) s(-1)) and five slope gradients (e.g., 5.24, 8.75, 17.63, 26.79, and 40.40 %). The results revealed that the ranges of Kr and tic for no biochar treatments varied from 0.1947 to 0.2107 s m(- 1) and 1.6971-1.7314 Pa, with the averaged values of 0.2007 s m(-1) and 1.7100 Pa, respectively. Compared with no biochar addition, the addition of 1-4 % biochar after 1-2 years generally resulted in a reduction in Kr ranging from 20 % to 59%, while increasing tic by 2-4 %. Conversely, 5.5 and 7% biochar addition increased Kr by 31 and 5%, and reduced tic by 12 and 6%. All biochar treatments after 3 years resulted in a 51 % reduction in Kr and a 5% increase in tic relative to bare soil, showing an increasing trend with an increasing biochar addition rate. The fluctuations in Kr and tic could be elucidated by changes in cohesion (COH) and mean weight diameter of soil aggregates (MWD), with COH (total effect of -0.32 and 0.17, P<0.01) and MWD (total effect of -0.13 and 0.37, P<0.01) serving as reliable estimators of Kr and tic during the 1-2 years following biochar addition. After biochar addition for 3 years, total organic carbon (TOC) (total effect of -0.45 and 0.10, P<0.01) emerged as a significant factor influencing Kr and tic, making TOC a potential predictor of Kr and tic. The results demonstrate that biochar may be an effective measure for enhancing soil resistance to erosion on the Loess Plateau, especially when applied over the long term.