Abstract: Background Severe land desertification in northwest Liaoning Province has led to significant soil erosion and ecological degradation, posing substantial constraints to regional sustainable development and ecological civilization construction. A comprehensive investigation of preferential flow characteristics in grasslands with varying desertification levels is crucial for optimizing water resource utilization and guiding ecological rehabilitation efforts in this region. Methods This study systematically examines soil preferential flow patterns across different desertification gradients in northwest Liaoning grasslands using dye-tracing experiments. We quantitatively analyzed both horizontal and vertical distribution characteristics of preferential flow, evaluated morphological variations in dye infiltration patterns, and elucidated the effects of desertification intensity on preferential flow dynamics. Results 1) Horizontal preferential flow distribution in desertified grasslands exhibited predominantly bimodal patterns with notable asymmetry. 2) The dye-stained area ratio decreased with increasing soil depth, with matrix flow depths ranging from 10.22 to 27.78 cm, maximum infiltration depths of 54.78-56.11 cm, and stained area ratios between 46.80% and 63.87%. 3) While the 0-50 cm soil layer showed relatively stable variation coefficients for stained area ratios, values increased markedly below 50 cm, indicating enhanced preferential flow variability. Vertical dye patterns transitioned through four distinct zones: stable, semi-active, active, and rapid-transition. 4) Stained area ratios demonstrated highly significant positive correlations (P<0.01) with root system parameters (r=0.31-0.65), with root diameter emerging as the most influential factor governing preferential flow development. Conclusions Grassland desertification will reduce the activity of soil preferential flow, and the root system is the main factor affecting the preferential flow of desertified grasslands in northwest Liaoning.