Abstract: In view of the failure phenomenon of wind turbine with crack damage during operation,the shear flow was taken as the inlet condition,and the stress distribution law of wind turbine blade with different forms of crack damage was analyzed based on the principle of fluid-structure coupling. Through the field experiment of UAV（unmanned aerial vehicle）,it was found that the cracks were mainly concentrated in the blade root（r/R = 0.10 section）and the trailing edge of the blade middle（r/R = 0.50 section）. The stress of single blade reaches the maximum at 30° azimuth angle,and the crack stress at blade root reaches the maximum at rated wind speed,which is33.34 MPa. Under strong wind speed,the crack force distributed in the blade is the maximum,which is 44.31 MPa. The gravity load mainly affects the force at the root of the blade,while the aerodynamic load mainly acts on the blade. The higher the wind speed is,the easier the crack in the middle part of the blade is to propagate. At the same time,the crack distributed along the chord has the strongest growth tendency. For the crack at the blade root,if the blade fails,the crack length shall be 1/2 of the chord length and the depth shall reach 1/2 of the blade thickness;for the crack at the middle of the blade,if the blade fails,the crack length shall reach 3/8 of the chord length and the depth shall reach 1/3 of the blade thickness.