Abstract: Aluminium based laminated materials were applied to investigate the fatigue crack propagation behavior of L-T(penetrating crack like)orientation by the methods of high frequency fatigue test,SEM and optical microscopy.The influence of interface bonding strength and plastic-elastic mismatch on the fatigue crack propagation behavior was considered.Analyzses with fracture mechanics theory showed that fatigue crack propagation rate of laminate was different from that of bulk materials as a result of plastic-elastic mismatch of component materials.The fatigue crack growth behavior in L-T orientation of bimetal plates can be predicted by the rule of averages according to that of their components.In other words,the fatigue crack growth rates tend to be closer of two single materials with different fatigue properties after being made into a bimetal plate.Multi-lamination interface bonding toughness was the main toughening mechanism of interface bonding strength.The toughening effect varied with the bonding strength.