The microstructure and room temperature mechanical properties of K4750 superalloy prepared by gravity casting and centrifugal casting were investigated, which included the second phase distribution, grain size, element segregation, distribution of shrinkage defects, room temperature mechanical properties and fracture morphology. It was found that the as-cast K4750 superalloy had similar microstructures prepared by two casting methods, namely γ matrix phase, MC-type carbide within grains, fine and dispersed γ" phase, as well as MC-type and M23C6 type carbides at grain boundary. However, these precipitates size were found to be more refined in the centrifugal casting methods. The average grain size of as-cast K4750 superalloy also decreased from 4.52 mm in the gravity casting to 2.22 mm in the centrifugal casting. Meanwhile, the area fraction of shrinkage defects was reduced from 1.75% in the gravity casting to 0.27% in the centrifugal casting. The dendrites of the gravity casting superalloy arranged neatly, whereas the dendrites of centrifugal casting superalloy were broken, and the segregation of elements was reduced. The K4750 superalloy samples prepared by centrifugal casting exhibited excellent room temperature mechanical properties, with yield strength, ultimate tensile strength and elongation of 632 MPa, 938 MPa and 11.2%, respectively. Compared with the K4750 superalloy prepared by gravity casting, its ultimate tensile strength increased by 20.6%, which may attributed to the combination of grain refinement, γ" phase refinement and casting defects reduction.