Drainage pipes, as infrastructure, have a direct impact on the quality of residents' lives due to their molding quality, which is why the requirements for the molding quality of drainage pipes are becoming increasingly stringent. Taking polyvinyl chloride (PVC) building drainage pipes as the research subject, and considering the melt temperature, holding pressure, mold temperature, and cooling time as four experimental variables, with the warpage deformation of the drainage pipe as the response target, an L₉(3⁴) orthogonal test was established. The results indicated that the melt temperature had a significant effect on the warpage deformation of the part. When the melt temperature, mold temperature, holding pressure, and cooling time were set at 180°C, 60°C, 70 MPa and 10 s, respectively, the warpage deformation of the part was relatively small, at 2.624 0 mm. The optimized process parameters were verified using Moldflow mold flow analysis software, and the results met the actual production requirements.