Abstract: The filling ability of semi-solid slurry is crucial to the mechanical properties of castings. In this study, the effects of forming temperature, injection pressure, mold temperature, and holding time on the filling distance of AZ91D semi-solid slurry were systematically investigated. The flow behavior of the semi-solid slurry and the influence of filling distance on mechanical properties were clarified. The experimental results indicate that the optimal filling quality is achieved at a forming temperature of 595-600 °C, a mold temperature of 230–250 °C, an injection velocity of 2.0–2.3m/s, and a holding time of 1.0 s. The results also show that both excessively short and excessively long distances from the injection gate are detrimental to the mechanical properties.