A communication device for handling a channel access procedure, comprising: a storage device; and a processing circuit, coupled to the storage device, wherein the storage device stores, and the processing circuit is configured to execute, instructions of: receiving a system information, SI, broadcasted by a first cell of a first base station, BS, wherein the SI configures a first energy detection threshold; performing a first channel access procedure on a first unlicensed carrier according to the first energy detection threshold; receiving a handover command from the first BS on a radio resource control, RRC, connection with the first BS, wherein the handover command configures a second energy detection threshold and indicates a second cell of the first BS or a second BS to be handed over to by the communication device; determining the second energy detection threshold according to a second absolute maximum energy detection threshold value indicated in the handover command or according to a second offset to a default maximum energy detection threshold value indicated in the handover command; and pe rforming a second channel access procedure via the second cell on a second unlicensed carrier according to the second energy detection threshold. a storage device; and a processing circuit, coupled to the storage device, wherein the storage device stores, and the processing circuit is configured to execute, instructions of: receiving a system information, SI, broadcasted by a first cell of a first base station, BS, wherein the SI configures a first energy detection threshold; performing a first channel access procedure on a first unlicensed carrier according to the first energy detection threshold; receiving a handover command from the first BS on a radio resource control, RRC, connection with the first BS, wherein the handover command configures a second energy detection threshold and indicates a second cell of the first BS or a second BS to be handed over to by the communication device; determining the second energy detection threshold according to a second absolute maximum energy detection threshold value indicated in the handover command or according to a second offset to a default maximum energy detection threshold value indicated in the handover command; and pe rforming a second channel access procedure via the second cell on a second unlicensed carrier according to the second energy detection threshold. receiving a system information, SI, broadcasted by a first cell of a first base station, BS, wherein the SI configures a first energy detection threshold; performing a first channel access procedure on a first unlicensed carrier according to the first energy detection threshold; receiving a handover command from the first BS on a radio resource control, RRC, connection with the first BS, wherein the handover command configures a second energy detection threshold and indicates a second cell of the first BS or a second BS to be handed over to by the communication device; determining the second energy detection threshold according to a second absolute maximum energy detection threshold value indicated in the handover command or according to a second offset to a default maximum energy detection threshold value indicated in the handover command; and pe rforming a second channel access procedure via the second cell on a second unlicensed carrier according to the second energy detection threshold.