Conventionally, rail transit castings have been fabricated from low-grade ductile iron (QT400~QT600). This paper focused on the research and development of rail transit housing castings made of high-grade austempered ductile iron (QT800-10). The process design of rail transit housing casting was carried out via the simulation software MAGMA and optimized via the addition of chills. Through microstructure examination, hardness testing, tensile strength testing, and other methods, the influence of different alloying elements on the microstructure and properties of the casting was investigated. The research results indicate that when the alloy composition is 3.65 wt.% C, 2.52 wt.% Si, 0.38 wt.% Mn, and 0.44 wt.% Cu, along with 0.15 wt.% bismuth-containing inoculant, the tensile strength, yield strength, and elongation of the sample reach peak values. After austempering, the casting properties are enhanced, meeting the standard requirements of customers.