An uplink data transmission method, comprising: receiving, by a terminal device, an uplink grant from a base station; and sending, by the terminal device, a report to the base station, wherein the report comprises a power headroom of at least one bandwidth part of a plurality of bandwidth parts, wherein a serving cell for the terminal device in a process of performing multi-connectivity communication comprises a plurality of medium access control, MAC, entities, wherein if the terminal device and the base station are in a same MAC entity, the report includes second bitmap information, and the second bitmap information is used to indicate a power headroom, PH, set corresponding to a type 1/3. and if the terminal device and the base station are not in a same MAC entity, the report includes third bitmap information and fourth bitmap information, where the third bitmap information is used to indicate a PH set corresponding to a type 1/3 in a MAC entity in which the terminal device is located, and the fourth bitmap information is used to indicate a PH set corresponding to a type 2 in the MAC entity in which the terminal device is located and the method further comprises: activating, configuring, or reconfiguring,, by the terminal device, at least one of the following that correspond to a first MAC entity in the plurality of MAC entities: a bandwidth part, and an uplink shared channel; and triggering, by the terminal device, a report on each of the plurality of MAC entities, or triggering a report only on a first MAC entity. receiving, by a terminal device, an uplink grant from a base station; and sending, by the terminal device, a report to the base station, wherein the report comprises a power headroom of at least one bandwidth part of a plurality of bandwidth parts, wherein a serving cell for the terminal device in a process of performing multi-connectivity communication comprises a plurality of medium access control, MAC, entities, wherein if the terminal device and the base station are in a same MAC entity, the report includes second bitmap information, and the second bitmap information is used to indicate a power headroom, PH, set corresponding to a type 1/3. and if the terminal device and the base station are not in a same MAC entity, the report includes third bitmap information and fourth bitmap information, where the third bitmap information is used to indicate a PH set corresponding to a type 1/3 in a MAC entity in which the terminal device is located, and the fourth bitmap information is used to indicate a PH set corresponding to a type 2 in the MAC entity in which the terminal device is located and the method further comprises: activating, configuring, or reconfiguring,, by the terminal device, at least one of the following that correspond to a first MAC entity in the plurality of MAC entities: a bandwidth part, and an uplink shared channel; and triggering, by the terminal device, a report on each of the plurality of MAC entities, or triggering a report only on a first MAC entity. activating, configuring, or reconfiguring,, by the terminal device, at least one of the following that correspond to a first MAC entity in the plurality of MAC entities: a bandwidth part, and an uplink shared channel; and triggering, by the terminal device, a report on each of the plurality of MAC entities, or triggering a report only on a first MAC entity.