Viscosity and yield stress have an important influence on the leveling performance of HTPB (Hydroxy-terminated polybutadiene) propellant slurry. In this study, through the leveling experiment of propellant slurry, it is concluded that slurry viscosity is the key criterion affecting leveling time and the influence law of yield stress on stagnation angle. At the same time, the leveling process of slurry is simulated by Carreau viscosity model and compared with the experimental results, and the effects of viscosity and yield stress on leveling performance were quantitatively characterized by computational fluid dynamics software CFD (Computational Fluid Dynamics). The results show that the error between the numerical simulation and experimental results of slurry flow angle at different leveling times is less than 7%, which verifies the feasibility of Carreau viscosity model to solve the slurry leveling process. The relationship between the flow angle of the studied slurry in the leveling tester and the natural logarithm of the slurry leveling time is close to linear. Univariate analysis was carried out on the viscosity of the slurry. When the viscosity increased from 400Pa·s to 1000Pa·s, the time required for slurry leveling increased from 315s to 825s; Univariate analysis was carried out on the yield stress of the slurry. When the yield stress increased from 60Pa to 120pa, the corresponding stagnation angle increased from 8.69°to 14.98°, with a corresponding increase of 72.4%.