Verticillium dahliae Kleb., which is a widespread and destructive cotton fungal pathogen, leads to vascular wilt diseases and spreads through soil and long-distance seed transmission.Verticillium wilt leads to large losses of cotton production all over the world, especially China.Lack of knowledge in molecular pathogenic mechanism of this causal cotton disease resulted in difficulty to control.To clarify the molecular mechanism, a mutant library containing 3000 transformants of a high virulent and microsclerotia producing V.dahliae strain Vd080 was constructed by the Agrobacterium tumefaciens mediated transformation method.