Abstract: To investigate the effect of parameters of sloping plate on the microstructure of semi-solid9Cr18, so as to lay the foundation of its thixoforming, a self-designed sloping plate is used to make 9Cr18semi-solid billets, and specimens for microstructural characterisation are cut from the core section of the billets.Resultsshow that as the length of the sloping plate increases from 350 mm to 840 mm, equivalent diameter of the primary grains is reduced from 53. 4 μm to 44. 9 μm, and the shape factor slightly increases from 0. 82 to 0. 84. However, after the length reaches 595 mm, its increase has little effect on the morphology of the primary grains. As the tilt angle increases in the range of 35 °-55 °, the equivalent diameter of primary grains increases from 50. 5 μm to 70. 8 μm, and the shape factor decreases from 0. 83 to 0. 75 because of lack of stirring time. Besides, the grains in released-quenched billets are finer than those in air-cooled billets.