Biaxial compression tests with an abrupt strain path change have been performed on polycrystalline aluminum to investigate the plastic deformation behavior under complex strain histories. Attentions are paid especially to the rapid change in the normal stresses due to the abrupt strain path change. The influences of the prestrain amplitude and the angular relation of sequential strain paths on the stress changes were also studied. The results showed that the transient increase of the normal stresses related to the latent hardening phenomenon with strain path change as well as the plastic anisotropy increase with the pre-straining amplitude. The transient increase in the stress was also affected by the strain histories in the sequential compression tests with the strain path change. The transient stress increment became large to the maximum then decreases with the angle between the sequential paths.