A control information transmission method, comprising: determining, by a terminal device, a bit length of downlink control information, DCI, based on a location of a target first time unit in a second time unit, wherein the DCI comprises time domain resource location information, the time domain resource location information is used to indicate at least one of time domain length information of a third time unit and time domain start location information for data transmission scheduled based on the DCI, the DCI is carried in the target first time unit, and a time domain length of the third time unit is less than or equal to a time domain length of the second time unit; and receiving, by the terminal device, the DCI from a network device; characterized in that the determining, by a terminal device, a bit length of DCI based on a location of a target first time unit in a second time unit comprises: determining, by the terminal device, a bit length of the time domain resource location information in the DCI based on the location of the target first time unit in the second time unit and a first mapping relationship, wherein the first mapping relationship is used to indicate a correspondence between an index of the location of the target first time unit in the second time unit and the bit length of the time domain resource location information in the DCI; and determining, by the terminal device, the bit length of the DCI based on the bit length of the time domain resource location information in the DCI. determining, by a terminal device, a bit length of downlink control information, DCI, based on a location of a target first time unit in a second time unit, wherein the DCI comprises time domain resource location information, the time domain resource location information is used to indicate at least one of time domain length information of a third time unit and time domain start location information for data transmission scheduled based on the DCI, the DCI is carried in the target first time unit, and a time domain length of the third time unit is less than or equal to a time domain length of the second time unit; and receiving, by the terminal device, the DCI from a network device; characterized in that the determining, by a terminal device, a bit length of DCI based on a location of a target first time unit in a second time unit comprises: determining, by the terminal device, a bit length of the time domain resource location information in the DCI based on the location of the target first time unit in the second time unit and a first mapping relationship, wherein the first mapping relationship is used to indicate a correspondence between an index of the location of the target first time unit in the second time unit and the bit length of the time domain resource location information in the DCI; and determining, by the terminal device, the bit length of the DCI based on the bit length of the time domain resource location information in the DCI. determining, by the terminal device, a bit length of the time domain resource location information in the DCI based on the location of the target first time unit in the second time unit and a first mapping relationship, wherein the first mapping relationship is used to indicate a correspondence between an index of the location of the target first time unit in the second time unit and the bit length of the time domain resource location information in the DCI; and determining, by the terminal device, the bit length of the DCI based on the bit length of the time domain resource location information in the DCI.