The influence of pouring length on the rheo-die casting microstructure and properties of AlSi9Mg have been researched by rheo-die casting method after semi-solid AlSi9Mg alloy melt prepared into by incline cooling and shearing device. The results show that the pouring length has great influence on the tensile strength and the elongation percentage, but little on the hardness and the impact toughness. When the pouring length is 500mm, the tensile strength is 290MPa, the elongation percentage is 4.1%, the hardness is 77.9HBS and the impact toughness is 0.72kJ/m².After rheo-die casting, the grain size of AlSi9Mg becomes smaller significantly and the shape becomes more round. When the pouring length is 500mm, the average diameter of primary solid phase is 7.1μm and the shape factor is 0.73.