The invention discloses a cigarette length detection method capable of eliminating metal exterior interference, which belongs to the technical field of cigarette length detection. The method comprisesthe steps that a complete outline of a cigarette is acquired; the position of a metal exterior is acquired; and if the cigarette outline is fractured during a test process, the effect of the metal exterior is eliminated by using the preserved position of the metal exterior. According to the method provided by the invention, the interference of the metal exterior is eliminated, and the length of the cigarette is accurately acquired.