The present invention provides a method and apparatus for processing uplink control information (UCI) and a method for transmitting the UCI based on a multiple input multiple output system, which processing method comprises: repeating ACK/NACK source bits and/or rank indicator (RI) source bits in the uplink control information to form M groups, with each group corresponding to a code word (S302), wherein M is the total number of code words; carrying out channel encoding on the ACK/NACK source bits and/or RI source bits of each code word to obtain QACK*Li output bits (S304), wherein QACK is the channel encoding output bits corresponding to each layer in a certain code word, L is the total number of layers, and the layer number corresponding to the i-th code word is Li; and multiplexing and interleaving the output bits and the data bits of the corresponding code word (S306). The present invention solves the problems of transmission and channel encoding of the ACK/NACK and/or RI in the multiple input multiple output (MIMO) system, and at the same time takes into account high load situations and backward compatibility.