This study investigates the optimization of semisolid thixoforming of A356 alloy using the cooling slope (CS) casting technique. By systematically varying process parameters such as pouring temperature, tilt (slop) angle, and cooling length, were explored their influence on the microstructure features of the cast alloy. The Taguchi method was employed to design experiments, and the results were analyzed using analysis of variance (ANOVA). In addition, the ANOVA was used to figure out the effect of CS casting process parameters on the microstructural characteristics. The findings demonstrate that cooling length significantly impacts the shape factor of primary α-Al grains, while pouring temperature primarily affects their size. Optimal conditions, 30° tilt angle, 350 mm cooling length and 620 ºC pouring temperature, were identified to achieve an average grain size of 17.14 μm and a shape factor of 0.9844. These findings contribute to a better understanding of CS casting and provide valuable insights for optimizing the production of thixoformed A356 alloy components.