Multiform resistance switching (RS) effects, including two modes of bipolar RS effects and unipolar RS effect, have been observed in the same Al/La0.7Ca0.3MnO3 (LCMO)/Pt structures by adjusting the thickness of Al electrode and implementing a forming process. When Al electrode is ultrathin (10 nm), a polarity reversal in bipolar RS can be obtained. The conversion from bipolar RS to unipolar RS can also be realized while increasing the thickness of Al (such as 50 nm). The transitions between these multiform RS effects derive from the changes in the Al/LCMO interface, which highlights the importance of the interface structure on the RS properties.