A method for transmitting downlink control information, terminal device and network device are provided. The method includes: a terminal device determines a plurality of candidate resource sets for transmitting first control information; the terminal device detects the first control information sent by a network device in the plurality of candidate resource sets; the terminal device determines a target resource set in the plurality of candidate resource sets according to a detection result of the first control information; the terminal device determines a target control channel resource corresponding to the target resource set according to the target resource set and a first mapping relationship, wherein the first mapping relationship is used for indicating a corresponding relationship between the plurality of candidate resource sets and a plurality of control channel resources; and the terminal device detects second control information sent by the network device in the target control channel resource.