In order to explore the effects of biological crusts coverage, slope and flow rate on soil detachment capacity under freeze-thaw conditions when biological crusts existed, the algal crusts in the Dongliugou small watershed in the northern Loess Plateau were taken as the research object. A test method combining indoor freeze-thaw simulation and scour were carried out, and Taguchi method and Orthogonal design were used to analyze the effects of algal crust coverage, slope, flow and freeze-thaw on soil detachment capacity. The results showed that when the soil detachment capacity was the maximum, the crusts coverage, slope, flow was 10%, 20° and 24 L/min, respectively, while the number of freeze-thaw times was 1 and 10 in Taguchi method and Orthogonal design, respectively. Under freezing and thawing conditions, with the increasing of algal crust coverage, the soil detachment capacity gradually decreased. Soil detachment capacity increased with the increasing of slope and flow. In the orthogonal design, soil detachment capacity firstly decreased and then increased, but in the Taguchi method, the change of soil detachment capacity did not have had obvious law with the increasing of freeze-thaw times under the experimental conditions. Slope was the main factor affecting soil separation ability in the Orthogonal design, and the contribution rate of each factor was slope (15.08%)>coverage (14.38%)>flow (13.69%)>freeze-thaw (-13.23%). In Taguchi method, algal crust coverage was the main factor affecting soil detachment capacity, and the contribution rate of each factor followed the order of coverage (30.41%)>slope (25.32%)>flow (1.59%)>freeze-thaw (0.85%). The relative error of the soil separation ability predicted by the Taguchi method was small (CV=0.49), and the coefficient of determination was large (R²=0.961>0.958, p≤0.001). Taguchi method could be used to predict soil detachment capacity under certain experimental conditions. The results could provide a theoretical reference for soil erosion research on the northern Loess Plateau.