A method for transmitting channel status information (CSI) of downlink multi-carrier transmission includes generating the CSI including at least one of a rank indicator (RI), a first precoding matrix index (PMI), a second PMI and a channel quality indicator (CQI) for one or more downlink carriers, the CQI being calculated based on precoding information determined by a combination of the first and second PMIs, determining, when two or more CSIs collide with one another in one uplink subframe of one uplink carrier, a CSI to be transmitted on the basis of priority, and transmitting the determined CSI over a uplink channel. If a CSI including an RI or a wideband first PMI collides with a CSI including a wideband CQI or a subband CQI, the CSI including a wideband CQI or a subband CQI has low priority and is dropped.