Abstract: The damage cause of torsion fatigue rotor blade and trial run rotor blade were studied throngh macro-examination,nondestructive testing,inside defect observation,mechanical property testing of polyurethane foam and FTIR analysis in this article.The results show that the existence of inner original pores has little effect on the bearing capacity,the failure crack of torsion fatigue rotor blade results from fatigue when the torsion test is over the fatigue life of the rotor blade,and the excess isocyanate in the foam result in the failure of trial run rotor blade cracks and lower mechanical property.