1. A buffer status reporting method, comprising: classifying, by a sending node comprising a Packet Data Convergence Protocol (PDCP) entity and at least two Radio Link Control (RLC) entities associated with the PDCP entity, the at least two RLC entities as at least one first RLC entity and at least one second RLC entity; generating, by the sending node and when a buffer of the first RLC entity comprises to-be-sent data, a first buffer status report (BSR) based on a size of the to-be-sent data in the buffer of the at least one first RLC entity; and sending, by the sending node, the first BSR to a receiving node corresponding to the at least one first RLC entity.