Large-scale and complex thick-walled titanium alloy casing castings are the key bearing component in heavy-duty gas turbine. Characterized by their large contour size, complex shapes, and substantial wall thicknesses, these castings often suffer from hard monolithic molding, complex metallurgical defects, and low dimensional accuracy compared to standard castings, limiting the assembly and use of high-power gas turbines. The solidified temperature field and fluid field during centrifugal investment casting process were systematically investigated using the finite element method. According to the characteristics of centrifugal casting, the mathematical models for designing spiral runner and inclined riser are derived. Simulation results confirmed the potential isolated liquid region range, a leading to the development of an integrated pouring system structural model capable of collecting exhaust gases and slag, regulating flow, and optimizing the temperature field, thereby significantly reducing solidification defects in castings. Furthermore, a symmetrically structured wax mold splicing scheme was designed, and a wax mold tree group for the pouring system was constructed, including a straight runner, cross runner, and inner runner with cross-sectional area ratios of 1:2.5:6. Additionally, to address the dimensional stability and insufficient strength of the investment ceramic shell, a reinforcing tool was developed. Based on this research, high-quality castings with complete filling, good metallurgical quality, and accurate size were achieved through the trial casting process. This work provides effective technical guidance for the manufacturing of titanium alloy casings in heavy-duty gas turbines, and the pouring system configuration offers reference value for other large-scale titanium alloy centrifugal investment castings.