In the Wire Arc Additive Manufacturing (WAAM) process of aluminum alloys, abnormal metallurgical behavior leads to defects in the material, such as porosity, cracks, and large grain sizes with varying directions and orientations, resulting in poor mechanical properties of the product. This paper discusses further research on Friction Stir Processing (FSP) applied to the surface of aluminum alloys after WAAM, aiming to minimize material defects and break down coarse grains to enhance the mechanical properties. Test specimens were produced through a hybrid manufacturing process combining WAAM and FSP on the formed material ultrasonic testing, tensile testing, and metallography were conducted to observe changes in microstructure and mechanical properties of the test material. Ultrasonic testing demonstrated the material's uniform density and detected minimal defects, indicative of high-quality integrity. From the tensile test results, it was found that the sample material's ultimate tensile strength and yield strength increased compared to the initial condition. Metallographic testing also provided visual evidence that FSP treatment caused most grains to undergo plastic deformation and dynamic recrystallization, resulting in finer grain sizes and improved mechanical properties. From a series of test results, it can be concluded that FSP is a highly effective technique for improving the microstructure and mechanical properties of WAAM-produced aluminum alloys © Published under licence by IOP Publishing Ltd.