The electroplating process is the best way to manufacture a telescope barrel (nickel shell), which makes it reliable to achieve separation of the nickel shell from the mold based on the principle of thermal expansion and contraction of materials. The difference in coefficients of thermal expansion between nickel and aluminum alloy is exploited to create a demolding gap between the nickel shell and the mold at low temperatures to ensure that the nickel shell is separated. However, if the demolding temperature is too low, irreparable deformation of the nickel shell may occur. In contrast, if the temperature is not low enough, the demolding is not thorough enough, so that the nickel shell and the mold are not completely separated, and then the mandatory demolding will cause local damage to the inner surface of the nickel shell. Therefore, in this paper, the demolding temperature is optimized with the help of the finite element method to achieve effective demolding of the nickel shell, which will reduce the trial and error rate and the manufacturing cost.