A communication device for handling a bearer type change in accordance with a third generation partnership project, 3GPP, fifth-generation, 5G, wireless communication system, the communication device comprising: at least one storage device; and at least one processing circuit, coupled to the at least one storage device, wherein the at least one storage device stores, and the at least one processing circuit is configured to execute, instructions of: receiving a first radio resource control, RRC, message on a signaling radio bearer, SRB, from a first base station, BS, wherein the first RRC message configures a data radio bearer, DRB, which is a master cell group, MCG, bearer type, and configures a first packet data convergence protocol, PDCP, configuration for the DRB; transmitting a first RRC response message to the first BS on the SRB, in response to the first RRC message; establishing a PDCP entity for the DRB according to the first PDCP configuration; transmitting a first plurality of PDCP Service Data Units, SDUs, to the first BS according to the PDCP entity and a TX_NEXT associated to the PDCP entity; receiving a second RRC message on the SRB from the first BS, wherein the second RRC message configures the MCG bearer type of the DRB to a secondary cell group, SCG, bearer type or a split bearer type, and configures a second PDCP configuration for the DRB; transmitting a second RRC response message on the SRB to the first BS, in response to the second RRC message; reconfiguring the PDCP entity according to the second PDCP configuration; and transmitting a second plurality of PDCP SDUs to a second BS according to the PDCP entity and the TX_NEXT associated to the PDCP entity, while being connected to the first BS. at least one storage device; and at least one processing circuit, coupled to the at least one storage device, wherein the at least one storage device stores, and the at least one processing circuit is configured to execute, instructions of: receiving a first radio resource control, RRC, message on a signaling radio bearer, SRB, from a first base station, BS, wherein the first RRC message configures a data radio bearer, DRB, which is a master cell group, MCG, bearer type, and configures a first packet data convergence protocol, PDCP, configuration for the DRB; transmitting a first RRC response message to the first BS on the SRB, in response to the first RRC message; establishing a PDCP entity for the DRB according to the first PDCP configuration; transmitting a first plurality of PDCP Service Data Units, SDUs, to the first BS according to the PDCP entity and a TX_NEXT associated to the PDCP entity; receiving a second RRC message on the SRB from the first BS, wherein the second RRC message configures the MCG bearer type of the DRB to a secondary cell group, SCG, bearer type or a split bearer type, and configures a second PDCP configuration for the DRB; transmitting a second RRC response message on the SRB to the first BS, in response to the second RRC message; reconfiguring the PDCP entity according to the second PDCP configuration; and transmitting a second plurality of PDCP SDUs to a second BS according to the PDCP entity and the TX_NEXT associated to the PDCP entity, while being connected to the first BS. receiving a first radio resource control, RRC, message on a signaling radio bearer, SRB, from a first base station, BS, wherein the first RRC message configures a data radio bearer, DRB, which is a master cell group, MCG, bearer type, and configures a first packet data convergence protocol, PDCP, configuration for the DRB; transmitting a first RRC response message to the first BS on the SRB, in response to the first RRC message; establishing a PDCP entity for the DRB according to the first PDCP configuration; transmitting a first plurality of PDCP Service Data Units, SDUs, to the first BS according to the PDCP entity and a TX_NEXT associated to the PDCP entity; receiving a second RRC message on the SRB from the first BS, wherein the second RRC message configures the MCG bearer type of the DRB to a secondary cell group, SCG, bearer type or a split bearer type, and configures a second PDCP configuration for the DRB; transmitting a second RRC response message on the SRB to the first BS, in response to the second RRC message; reconfiguring the PDCP entity according to the second PDCP configuration; and transmitting a second plurality of PDCP SDUs to a second BS according to the PDCP entity and the TX_NEXT associated to the PDCP entity, while being connected to the first BS.