A method for indicating a state of Packet Data Convergence Protocol, PDCP, duplication data, wherein the method is applied to a terminal device, the terminal device has a first PDCP entity and a plurality of Radio Link Control, RLC, entities corresponding to the first PDCP entity, and the method comprises: receiving, by the terminal device, first indication information, wherein the first indication information is used for indicating a data behavior between the first PDCP entity and the plurality of RLC entities; wherein receiving, by the terminal device, the first indication information comprises: receiving, by the terminal device, an MAC CE format, wherein the MAC CE format comprises the first indication information; receiving, by the terminal device, second indication information, wherein the second indication information is used for indicating whether the first indication information is comprised in the MAC CE format, wherein receiving, by the terminal device, the second indication information comprises: receiving, by the terminal device, a reserved index in a Logical Channel Identifier, LCID, of a DownLink Shared Channel, DL-SCH, wherein the reserved index is used for indicating whether the first indication information is comprised in the MAC CE format; wherein receiving, by the terminal device, the first indication further comprises: receiving, by the terminal device, a second type of MAC CE, the second type of MAC CE is used for indicating a data behavior between an RLC entity and the first PDCP entity corresponding to a second DRB, wherein the second type of MAC CE is used for indicating a data behavior between the first PDCP entity corresponding to the second DRB and at least three RLC entities. receiving, by the terminal device, first indication information, wherein the first indication information is used for indicating a data behavior between the first PDCP entity and the plurality of RLC entities; wherein receiving, by the terminal device, the first indication information comprises: receiving, by the terminal device, an MAC CE format, wherein the MAC CE format comprises the first indication information; receiving, by the terminal device, second indication information, wherein the second indication information is used for indicating whether the first indication information is comprised in the MAC CE format, wherein receiving, by the terminal device, the second indication information comprises: receiving, by the terminal device, a reserved index in a Logical Channel Identifier, LCID, of a DownLink Shared Channel, DL-SCH, wherein the reserved index is used for indicating whether the first indication information is comprised in the MAC CE format; wherein receiving, by the terminal device, the first indication further comprises: receiving, by the terminal device, a second type of MAC CE, the second type of MAC CE is used for indicating a data behavior between an RLC entity and the first PDCP entity corresponding to a second DRB, wherein the second type of MAC CE is used for indicating a data behavior between the first PDCP entity corresponding to the second DRB and at least three RLC entities. receiving, by the terminal device, an MAC CE format, wherein the MAC CE format comprises the first indication information; receiving, by the terminal device, second indication information, wherein the second indication information is used for indicating whether the first indication information is comprised in the MAC CE format, wherein receiving, by the terminal device, the second indication information comprises: receiving, by the terminal device, a reserved index in a Logical Channel Identifier, LCID, of a DownLink Shared Channel, DL-SCH, wherein the reserved index is used for indicating whether the first indication information is comprised in the MAC CE format; wherein receiving, by the terminal device, the first indication further comprises: receiving, by the terminal device, a second type of MAC CE, the second type of MAC CE is used for indicating a data behavior between an RLC entity and the first PDCP entity corresponding to a second DRB, wherein the second type of MAC CE is used for indicating a data behavior between the first PDCP entity corresponding to the second DRB and at least three RLC entities. receiving, by the terminal device, a reserved index in a Logical Channel Identifier, LCID, of a DownLink Shared Channel, DL-SCH, wherein the reserved index is used for indicating whether the first indication information is comprised in the MAC CE format; wherein receiving, by the terminal device, the first indication further comprises: receiving, by the terminal device, a second type of MAC CE, the second type of MAC CE is used for indicating a data behavior between an RLC entity and the first PDCP entity corresponding to a second DRB, wherein the second type of MAC CE is used for indicating a data behavior between the first PDCP entity corresponding to the second DRB and at least three RLC entities.