The embodiment of this invention discloses a method, a system and an apparatus for admission control of multicast or unicast. The method for admission control of multicast comprises: a network device receives a multicast request and executes admission control operation of multicast resources according to the multicast request; when multicast resources are not sufficient, the network device sends an outer resources request to a resources admission control device, and executes multicast operation according to the results of admission control operation returned by the resources admission control device responsive to said outer resources request. The method for admission control of unicast comprises: a resources admission control device receives a unicast resources request and executes admission control operation of unicast resources according to the unicast resources request; when the unicast resources are not sufficient, the resources admission control device sends an outer resources request to a network device; the resources admission control device executes unicast operation according to the results of admission control operation returned by the network device responsive to said outer resources request. The embodiment of this invention guarantees fast handoff of multicast service channel in the case of implementing resources share of multicast services and unicast services, and the implementation is simple.