Provided are a method and an apparatus for determining transmission power of a preamble in a wireless communication system. A terminal estimates secondary cell (SCell) path loss with respect to a downlink (DL) component carrier (CC), which is in a linkage relationship with an uplink (UL) component carrier inside the SCell; decides the transmission power of a physical random access channel (PRACH) preamble based on the SCell path loss that is estimated; and transmits the PRACH preamble to a base station through the UL CC inside the SCell, based on the transmission power that is decided, wherein the SCell and a primary cell (PCell) comprises a carrier aggregation (CA) system, the PCell is a cell from which the terminal performs radio resource control (RRC) connection with the base station, and wherein the Scell is at least one cell from residual cells in the carrier aggregation excluding the PCell.