A state transition method of a wireless communication system is provided. A network transition request is transmitted by a wireless electronic device to a first base station of a first network. The network transition request includes an assistance information of the wireless communication device. A handover request including the assistance information is transmitted by the first base station to a second base station of a second network. A handover message is generated and transmitted by the second base station to the first base station in response to the handover request. A state transition message is generated and transmitted by the first base station to the wireless communication device in response to the handover message. The wireless communication device transitions from an RRC inactive state of the first network to a first state of the second network in response to the state transition message.