Taking a ZTi55A titanium alloy large-scale skeleton as the research object, through the method of segmental casting and welding, investment mould precision casting and posttreatment technology were systematically discussed. Three-stage split casting and welding processes are used to successfully prepare whole casts, and defects such as cracks are effectively controlled. The moulding quality of castings can be significantly improved by the reasonable design of wax mould preparation, shell preparation, melting pouring and subsequent pickling and repair welding processes. The results show that complete filling of the whole casting is successfully achieved, and the process parameters suitable for ZTi55A titanium alloy are determined. The α-brittle fouling layer is effectively removed during pickling. In addition, the proposed repair welding process can repair the solder joint crack and ensure the mechanical properties and dimensional accuracy of the casting.