Abstract: Background Few studies have been made to investigate the spatial distribution characteristics and evolution patterns of preferential flow from sloping farmland under varying tillage intensities in southwester alpine-canyon area. Methods In this study, consecutive tillage by hoeing was performed no-till, 1, 10, 20, 30, 40 and 15 times on a typical sloping farmland of the southwester alpine-canyon area, China, to simulate the impact of short- and long-term tillage on preferential flow properties at different slope positions. By combining field bright blue dyeing tracing experiments with image processing techniques, we systematically analyzed morphological characteristics of soil preferential flow and related parameter changes. Results Results demonstrated that with the increase of tillage intensity, the index of priority flow showed a trend of first increasing and then decreasing. When tillage was carried out continuously for 30 times, the development degree of priority flow was the best, with a staining area ratio of 87.52%, a priority flow length index of 583.08%, and the lowest staining coefficient of variation (0.33). When the number of tillage operations is less than 30 times, the infiltration depth and dyeing area ratio at the upper and middle slope positions are higher than those at the lower slope position. However, when the number of tillage operations exceeds 30 times, the preferential flow development degree at the lower slope position is higher. Besides, the variance contribution of tillage intensity to the coefficient of variation of dyeing, depth of matrix flow, length index and macroporosity is higher than that of slope position, indicating that tillage intensity is the dominant factor affecting the development of preferential flow. Research has confirmed that there is a critical threshold effect of tillage intensity on preferential flow (30 times). Appropriate reduction of tillage intensity can inhibit the development of preferential flow, which is conducive to regional soil and water conservation and sustainable agricultural development. These findings provide scientific basis for water and soil resource management and erosion prevention from sloping farmland in southwester alpine-canyon area, China.