The dynamic stress produced by fluid alternating load is the important factor of appearing blade cracks,which seriously affected the station safety and the stable operation of the unit.Based on analyzing the transient intensity of loading alternating dynamic stress,the dynamic stress amplitude of the defect blade and stress concentration phenomenon of defect location are studied.The stress concentration values of the defects at the defect turbine blade is calculated.Based on comparing the natural frequency difference between normal blade and defect blade and through CFD numerical calculation and intensity analysis of FEM,the dangerous points of maximum dynamic stress on this two kinds of blades appeared and the dynamic stress amplitude difference between them is compared.