The process parameters have a direct impact on the 3D printing quality of solid propellant grains. To more reasonably adjust the 3D printing process parameters and improve printing quality， based on the single-layer stacking process， a numerical simulation method was employed to conduct an orthogonal experimental study on three influencing factors： extrusion speed， printing height， and printing temperature. The degree of influence of each factor was calculated through variance and range analysis. The grey relational analysis method was adopted for comparison， and the optimal combination of process parameters was selected after comprehensively considering the printing accuracy of special points. A method for calculating the printing line spacing based on single-line cross-sectional data was proposed for the first time， and simulation and experimental verification were conducted. The results indicated that the extrusion speed had the greatest impact on printing quality. When the extrusion speed was set to 12 mm·s^-1， the nozzle height was 1.2 mm， and the printing temperature was 55 ℃， the printed part exhibited optimal quality. After parameter adjustment， the tensile strength of the specimen increased from 0.21 MPa to 0.43 MPa， and the density rose from 1.43×10³ kg·m^-³ to 1.65×10³ kg·m^-³. Single-layer printing simulations and experiments demonstrated a significant improvement in molding quality after parameter adjustment.