To satisfy various requirements restricted delegation of in grid applications, a hierarchical role-based delegation authorization execution model for service grid is proposed. The dynamic characteristic of delegation role granting or revocation and the associated constraint of delegation role granting are effectively supported. The fine-grained associated role dependency is implemented by adding trustworthiness. Partial delegation problem is easily solved by defining the role tree as the basic unit of delegation authorization and by pruning the role tree. The delegation spread tree with trustworthiness is defined to implement multi-step delegation in a fine-grained manner. The delegation certification is proposed to fully express temporary delegation, associated role delegation, partial delegation, multi-step delegation. Based on above works, a set of formal delegation authorization execution rules is proposed and proved, and the delegation authorization execution process is effectively controlled. The exhibited example shows that the model can satisty various requirements of restricted delegation in grid applications.