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Aim at the fatigue fracture fault of aero-engine directional solidified turbine blade, laser shock peening was suggested to be conducted on the DZ17G superalloy simulated blades to improve fatigue performance. However, in order to avoid the occurrence of grain refinement in the columnar crystals,a special laser shock treatment method, high frequency shock without ablation coating underwater based on micro-scale laser shock peening, was proposed. In this method, short laser pulse width micro-scale laser beam was conducted to decrease the plastically degree and affected depth, and high frequency shock without ablation coating was conducted to form a uniform plastically strengthening layer. The experiment results indicate that there are high density disloactions and dislocation tangles generated in the shallow layer of DZ17G superalloy simulated blade, but no grain refinement, and the density of dislocations decrease with the depth sharply. High density disloactions and dislocation tangles result in a high improvement of hardness, increased by 30%. However, There is a 180 thick hardened layer generated. The fatigue strength of DZ17G superalloy simulated blades is improved form 257.00 MPa to 302.00 MPa, increased by 17.5%. There is still a improvement of 11.7% on fatigue strength after thermal insulation for 2h under 800℃. High density disloactions and dislocation tangles are the immanent cause of fatigue performance improvement.