A method and terminal for feeding back channel state information are applied to a 4-antenna system. The method includes: a terminal acquiring channel state information, the terminal performing joint encoding on PMI1 information and RI information into a 4-bit or 5-bit feedback report, or, performing joint encoding on PMI1 information and PMI2 information into a 4-bit feedback report, or, the PMI2 information using 2-bit feedback; and the terminal feeding back the feedback report in a physical uplink control channel.