In Grid

it is an important strategy that using multicast to realize the large-scale information resource sharing.However

it is very difficult to ensure the security of multicast.In this paper

based on the basic principles of the centralized key distributed strategy and the distributed key distribution strategy

according to the multicast mechanism in Grid

considering the dynamic factors of multicast members

we present the member hierarchy method for key distribution

the member discovery protocol

the clustering protocol and the key distribution strategy

thus constituting the key distribution strategy of security multicast in Grid.In order to validate the feasibility and the availability of this strategy

a simulation experiment is done.The results show that it is feasible and efficient to ensure the security multicast in Grid.