The present invention relates to an interaction method and device between resource and admission control systems, which is applied in a case that a mobile user equipment accesses a network at a fixed network side and deploys a service of the fixed network, the method includes: the resource and admission control system of the fixed network performing, after receiving a resource request sent from an application function of the fixed network, an authorization check on the resource request, and interacting with the resource and admission control system of a mobile network to make the resource and admission control system of the mobile network perform another authorization check on the resource request; if both the authorization checks are passed, the resource and admission control system of the fixed network formulating final policy rules, and returning a resource response to the application function of the fixed network. The device comprises the resource and admission control system of the fixed network and the resource and admission control system of the mobile network. The method and device of the present invention can solve the resource and admission control problems when a mobile user equipment accesses the network at the fixed network side and deploys a service in the fixed network.