In order to improve the product quality and production safety, the single-screw extrusion molding process of propellant was analyzed. The propellant extrusion process in a single-screw extruder with smooth barrel and a single-screw extruder with slotted barrel was numerically simulated by finite element method. The conveying velocity, maximum pressure, mixing index and viscous heat in the flow field were compared. The influence of different barrel structures on conveying efficiency, mixing effect and safety performance were analyzed. The results showed that compared with the single-screw extruder with smooth barrel, the single-screw extruder with grooved barrel had better conveying performance and mixing effect, and the grooved barrel with 6 grooves and 2~3 mm groove depth was the optimal structure.