Taking the S818 airfoil of 1.5 MW wind turbine blade as the research object. Model of the finite element of airfoil flow field was built in this paper. The nonviscous incompressible Navierstokes equations are used as flow control equation, which conducted numerical simulation analysis on Icefree airfoil, airfoil of rime ice, chordlength ice, and horn ice. The pressure distribution are obtained from the liftdrag ratio, velocity vector and surface pressure of different thickness of the blade airfoil in the angle of attack from -2° to 20°.The results showed that the thicker of the ice coating, the shaper maximum liftdrag ratio of airfoil are decreased. Moreover, certain thickness of chord length ice and horn ice leads to the mutation of the loss of liftdrag ratio. When ice thickness is 10 mm, the maximum liftdrag ratio amplitude reduction of horn ice reached the maximum at 2204%, the chord length ice at 11.97% and rime ice at 6.14%. In addition, the airfoil after icing would enter stall area in advance which deteriorates aerodynamic performance of blade and reduces the power coefficient of wind turbine.