Abstract: Residual stress has an important impact on the mechanical properties of injection parts. Through an analysis using Moldflow it was known that increasing melt and mold temperatures, lowering injection rate, reducing packing time, and packing pressure were beneficial to reduce the residual stress. Subsequent industrial hydrostatic test verified the numerical simulation results, and found that the residual stress was seriously influenced by the melt and mold temperatures, while less affected by packing pressure, packing time, and injection rate.