Y-shaped tubes are key to the service life of spacecraft fuel delivery pipelines. Three-dimensional modelling software was used to conduct geometric modelling and structural analysis of the Y-shaped tube, of which the overall wall thickness was thin, and the three flanges and convex position were thick, leading to difficulty in filling the mold and the tendency to form cold shuts and other casting defects. The ProCAST simulation software was used to numerically simulate the Y-shaped tube during the investment casting process. By setting different pouring temperatures and mold shell temperatures, the metallurgical quality of castings under different process parameter schemes was studied and compared. The optimal process parameter scheme was selected to further improve the service life of the Y-shaped tube. The simulation results show that when the pouring temperature is 1 650 ℃ and the mold shell temperature is 350 ℃, the porosity of the casting is the smallest (1.42 cm3) at a 3% ratio, and the metallurgical quality of the casting is the best. The experimental verification of the process parameter scheme was then carried out. Through DR verification, a casting meeting the requirements of the relevant technical agreement is obtained, and the experimental results are consistent with the simulation results, which verifies the feasibility and accuracy of the simulation results.