Abstract: The fracture of journal in hub-arms of helicopter has been analyzed on the basis of fracture mechanics. For simplicity the journal can be regarded as a cylinder with a transverse surface crack under bending load. Taking the crack area S0 as a main parameter, we have obtained the compliance of the cylinder λ , the energy release rate G and the stress intensity factor KI from the experimental data.It was found that （da）/（dN） could not give a complete expression forthe features of the fatigue crack propagation in the cylinder with a transverse surface crack, so it was suggested to adopt the area rate of fatiguecrack propagation （ds）/（dN） = C （△W1）n for this purpose. The experimentalinvestigation on the fatigue surface propagation of different specimens confirmed this formula.The critical crack propagation area and the residual life expectancy of the journal were discussed on the basis of the theoretical analysis and experimental investigation. Structural fatigue tests verified that the results obtained by the presented method were in good agreement with tests data.