A revision level notification method and system for a mobile station is provided for facilitating a handover between networks of different generations. The revision level notification method for an inter-generation handover includes detecting a handover trigger event for a handover from a first network to a second network, setting a protocol version in association with the first network, receiving a classmark enquiry message from the second network, and transmitting a classmark change message containing a revision level of a mobile station obtained with reference to the protocol version to the second network in response to the classmark enquiry message.