Abstract: Based on low cycle fatigue critical damage behavior of materials, a numerical simulation method used to predict fatigue crack propagation behavior of materials and structures was presented, and this new method is named as LFF (LCF-Low Cycle Fatigue+FCP-Fatigue Crack Propagation +FEA-Finite Element Analysis). For LFF method, a set of ANSYS command streams for the numerical simulation algorithm were developed to determine the stress and strain amplitude of nodes located at the plastic zone in the direction of crack propagation and fatigue damage of these nodes can be obtained, furtherly, the fatigue crack propagation prediction can be realized by discontinuous crack propagation assumption. For steam turbine rotor material: Cr2Ni2MoV steel, Manson-Coffin critical damage model and Paris crack propagation model of Cr2Ni2MoV steel were obtained by tests on smooth uniaxial specimens and CT (compact tensile) specimens at room temperature respectively. Results show that LFF method has better accuracy to predict fatigue crack propagation behavior of complicated cracks of CT specimens.