Device and method of handling communication

A first base station (BS) of handling communication, comprising:

• a storage device, for storing instructions of:
• connecting to a communication device;
• transmitting an addition request to a second BS to request the second BS to allocate at least one radio resource for the communication device, when connecting to the communication device;
• receiving an addition request acknowledgement comprising a secondary cell group (SCG) configuration configuring a SCG for allocating the at least one radio resource for the communication device, from the second BS;
• transmitting a radio resource control (RRC) message to the communication device, wherein the RRC message comprises the SCG configuration;
• receiving a RRC complete message from the communication device, wherein the communication device transmits the RRC complete message in response to the RRC message;
• performing a determination of a release of the second BS for the communication device;
• generating a release request in response to the determination, wherein the first BS requests a data forwarding in the release request if the release is caused by at least one measurement result of the SCG, a handover, a SCG failure or a master cell group (MCG) failure, and does not request the data forwarding in the release request if the release is caused by a RRC connection release or a user inactivity;
• and
• transmitting the release request to the second BS;
• wherein the first BS determines that the user inactivity occurs, when the first BS has no data to be transmitted to the communication device and the first BS receives a buffer status report (BSR) indicating that no data is in a buffer of the communication device from the communication device;
• and
• a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device.