The present disclosure proposes a method for transmitting a buffer status report informing of the data to be transmit in uplink. The method for transmitting buffer status report of a terminal in a wireless communication system includes checking, when allocating uplink resource for new data transmission, whether first buffer status report triggered but not cancelled exists, generating, when the first buffer status report exists, uplink data including the buffer status report, checking whether second buffer status report triggered but not cancelled exist except for the buffers status report included in the uplink data, and determining whether to cancel the second buffer status report depending on whether the first buffer status report is a regular buffer status report or periodic buffer status report. With the proposed method, the terminal is capable of transmitting the padding BSR without extra cancellation operation, resulting in reduction terminal's operation complexity.