A method for sending control information, wherein the method comprises: determining, by a network device based on a first time-frequency domain resource for sending one piece of control information, at least one information field comprised in the piece of control information, wherein the first time-frequency domain resource is a time-frequency domain resource in a transmission time period that is shorter than or equal to 0.5 ms; determining, by the network device, a quantity of bits of the piece of control information based on the at least one information field; and sending, by the network device, the piece of control information based on determined quantity of bits to a user terminal on the first time-frequency domain resource, wherein a total quantity of bits sent by the network device to the user terminal is greater than or equal to the quantity of bits of the first control information; wherein when the first time-frequency domain resource for sending the piece of control information is a time-frequency domain resource beyond a first time region, the at least one information field comprises a second information field, information carried in the second information field is used to indicate a time-frequency domain resource not occupied by a downlink control channel, or used to indicate a time-frequency domain resource occupied by a downlink control channel, or used to indicate a time-frequency domain resource occupied by a downlink data channel, and the first time region is a time region to which first two symbols in a downlink subframe belong, or is a time region to which first three symbols in a downlink subframe belong, or is a physical downlink control channel, PDCCH, region; and when the first time-frequency domain resource for sending the piece of control information is in the first time region, the information domain of the piece of control information does not comprise the second information domain. determining, by a network device based on a first time-frequency domain resource for sending one piece of control information, at least one information field comprised in the piece of control information, wherein the first time-frequency domain resource is a time-frequency domain resource in a transmission time period that is shorter than or equal to 0.5 ms; determining, by the network device, a quantity of bits of the piece of control information based on the at least one information field; and sending, by the network device, the piece of control information based on determined quantity of bits to a user terminal on the first time-frequency domain resource, wherein a total quantity of bits sent by the network device to the user terminal is greater than or equal to the quantity of bits of the first control information; wherein when the first time-frequency domain resource for sending the piece of control information is a time-frequency domain resource beyond a first time region, the at least one information field comprises a second information field, information carried in the second information field is used to indicate a time-frequency domain resource not occupied by a downlink control channel, or used to indicate a time-frequency domain resource occupied by a downlink control channel, or used to indicate a time-frequency domain resource occupied by a downlink data channel, and the first time region is a time region to which first two symbols in a downlink subframe belong, or is a time region to which first three symbols in a downlink subframe belong, or is a physical downlink control channel, PDCCH, region; and when the first time-frequency domain resource for sending the piece of control information is in the first time region, the information domain of the piece of control information does not comprise the second information domain.