On the basis of the ProCAST finite element simulation platform, the TC18 titanium alloy pump vacuum condensing shell casting process was optimized. The difference in rheological properties between the TC18 and TC4 titanium alloys was quantitatively analysed by constructing a Newtonian fluid constitutive model, and the optimal pouring temperature of TC18 was determined to be 1 770 ℃. A three-dimensional fluid-solid coupling model of the pump body was established, and the filling behavior and solidification characteristics of the melt were systematically compared between the traditional top pouring system and the improved bottom pouring system. The results show that the turbulent flow of liquid metal (the flow rate decreases by 38.6%) is effectively restrained after the pouring system is optimized, and the volume fraction of shrinkage porosity is reduced by 74.3%. Moreover, the secondary dendrite spacing is reduced by 21.4%, and the tensile strength of key parts is increased by 15.5%. The reliability of the simulation results is verified via X-ray flaw detection and tensile tests.