By considering the frequent migration characteristic of mobile terminal and the existing delegation based RBAC, the delegation based cross-domain access control model in cloud computing of the mobile terminal is presented. This delegation model can solve the problems of the frequent migration. It makes the management node of each domain maintain a dynamic routing table to locate the node. Also, a synthetic method to obtain synthetic mapping role is proposed. By combining the quantified-role method, the delegated node obtains the final mapping role of this cross-domain requirement. This can effectively solve the problem of permission hidden ascension in the mapping. The requirement frequency threshold will avoid the risk which is caused by the malicious node's excessive operation. Analysis shows that the model has better security.