Disclosed are a method, a device and a system for transmitting control information, which relate to the field of communication technologies. In order to feed back response information in an application scenario of dynamic TDD subframe, the present invention provides the following technical solution: determining a subframe set corresponding to uplink subframe n, the subframe set comprising dynamic subframes; determining feedback response information according to the subframe set; and sending, in uplink subframe n, the feedback response information to a base station through a physical uplink channel, wherein n is a subframe serial number of the uplink subframe.