The complex of insect mycoses by entomopathogenic fungi includes, in general, spore adhering, cuticle penetration, hemocoel colonization and host death. Recent gene function studies of Metarhizium anisopliae and Beauveria bassiana have bettered the understanding of the mechanisms of molecular entomopathogenicity that there are different genes involved in different infection stages. With the identifications of different virulent genes and the exploring of exogenous toxins, genetic engineering works have been reviewed in this paper to demonstrate the potentials to improve the control efficacies of mycoinsecticides by the strategy of toxin gene overexpression. Future studies are discussed to further explore fungal virulent genes and their functions during infection processes.