Disclosed in the present application are a method and device for transmitting feedback information, used to define new feedback timing for downlink data using a dynamic and variable TTI length during transmission, so as to ensure that ACK/NACK feedback information of downlink data is fed back on an earliest uplink transmission resource meeting a processing delay requirement, thereby reducing system delay. The method for transmitting feedback information provided in the present application comprises: receiving downlink transmission; and determining, at least according to a TTI length and/or a second TTI length of the downlink transmission, an uplink time-domain resource position for ACK/NACK feedback information transmission for the downlink transmission, and sending, on the uplink time-domain resource position, the ACK/NACK feedback information for the downlink transmission, wherein the second TTI length is configured by configuration signaling or is a pre-arranged TTI length used for determining the uplink time-domain resource position of ACK/NACK feedback information transmission.