In recent years, the development and application of high voltage cables with smooth aluminum sheath have attracted much attention in China. Compared to corrugated aluminum sheaths, the mechanical properties of smooth ones are a focal point of industry interest. The smooth aluminum sheath is manufactured either by welding plates or by melt extrusion to form a loose tube, followed by diameter reduction through drawing or rolling process. As a result, its mechanical properties may be affected by the production process. In this paper, sheet samples with and without weld seams were taken circumferentially and axially from the welded or extruded smooth sheaths, which had undergone the roller pressing process. Then, the tensile strength, yield strength and elongation at break of the samples were tested and compared to assess the impact of the production process. Simultaneously, metallographic samples were prepared by cutting and polishing the aluminum sheets. After acid etching or alkali etching, the grain morphology and microstructure defects on the sample surface could be observed, providing insights into the reasons for changes in mechanical properties. The results indicate that for the welded sheath, the argon arc welding process and the presence of weld seams have minimal impact on the mechanical strength. However, both factors will reduce the plastic deformation property, especially in the direction perpendicular to the weld seam. The subsequent rolling treatment can improve the microstructure of the aluminum material, thereby mitigating the negative effects caused by the weld seam. For the extruded sheath, although its initial mechanical properties are excellent, the rolling process can deteriorate the grain size distribution, resulting in decreased strength and toughness. In summary, both types of aluminum sheaths exhibit outstanding mechanical strength, while the extruded one is better in plastic deformation performance.