A method for transmitting feedback information in a mobile communication system using Multiple Input Multiple Output (MIMO) is provided. The method includes, when knockdown precoding is used and Antenna Selection precoding is used, setting an index field for indicating a universal matrix of a precoding matrix of a first reverse feedback channel to a value indicating whether Antenna Selection Space Time Transmit Diversity (STTD) is present; when the knockdown precoding is used and the Antenna Selection precoding is used, writing antenna selection information in a vector bitmap field of the first reverse feedback channel; when the knockdown preceding is used and the Antenna Selection precoding is used, estimating Channel Quality Information (CQI) according to the antenna selection information and writing the estimated CQI in a CQI field of a second reverse feedback channel; when the knockdown precoding is used and the Antenna Selection precoding is used, inserting a predetermined value into a Rank field of the second reverse feedback channel; and transmitting a signal of the first feedback channel including the index field and the antenna selection information and a signal of the second feedback channel including the CQI field, to a base station.