In order to prepare gun propellants with complex geometries， the extrusion 3D printing process of double base gun propellants was proposed. Square-shaped， wheel-shaped， star hole-shaped and lace seven hole double base gun propellants were printed by screw extrusion gun propellants 3D printer. The surface structure， size uniformity， density and mechanical property of the printed gun propellants were characterized. The results show that the surface of the printed gun propellants is smooth without obvious defects. The size uniformity of lace seven hole gun propellants reaches the standard of traditional gun propellant preparation process， and the size uniformity of arc thickness for wheel-shaped gun propellant is good， with a standard deviation of 0.026 mm and a relative standard deviation of 0.92%. The density of square-shaped gun propellant is higher （1.567 g·cm^-3） than those of other gun propellants （1.549-1.559 g·cm^-3）. The tensile strength of gun propellant samples with concentric filling path （the filling line direction is parallel to the tensile direction） and straight line （the filling line direction is perpendicular to the tensile direction） are 14.467 MPa and 10.789 MPa， respectively， the former is equivalent to that of gun propellants prepared by traditional extrusion process. The good printing of multi geometry gun propellants with radians and angles provides a basis for the preparation of complex geometry gun propellants.