Embodiments of the present invention disclose a method, an apparatus, and a system for transmitting control information. The method includes: determining enhanced resource element group numbers in resource blocks, and determining, according to the resource element group numbers, positions of resource elements corresponding to enhanced resource element groups; interleaving the enhanced resource element group numbers, and determining an enhanced control channel element; determining, according to the enhanced control channel element and the positions of the resource elements corresponding to the enhanced resource element groups, positions of resource elements corresponding to the enhanced control channel element; and transmitting corresponding control information on the positions of the resource elements corresponding to the control channel element. The present invention alleviates a problem that channel frequency diversity is poor, and lowers the probability of loss of information of a terminal device.