A user equipment and a buffer status report (BSR) cancellation method are provided. In the method, the data duplication is activated on at least one data unit of packet data convergence protocol (PDCP). The data duplication works such that, in the carrier aggregation (CA), one data unit corresponds to at least two component carriers provided by a base station supporting integrated access and backhaul (IAB) mechanism. For each data unit, at least two BSRs are triggered, and each BSR corresponds to one logical channel. Then, at least one BSR is canceled according to a canceling condition. Accordingly, the IAB network can be applied with multiple BSR cancellation.