An information transmission method performed by a wireless access device, comprising: determining time information used to instruct a terminal device to detect information transmitted by the wireless access device to the terminal device on a second band, comprising determining a candidate timeslot corresponding to a time segment in which the information is sent on the second band, wherein the time information includes a first duration and a second duration, the first duration is a duration in which the terminal device detects the information transmitted by the wireless access device on the second band, the second duration is a first time interval between a moment at which the terminal device receives the instruction message and a moment at which the terminal device starts to detect the information transmitted by the wireless access device on the second band, and the second duration is less than or equal to a second time interval between the moment at which the terminal device receives an instruction message and a start moment of the candidate timeslot; sending the instruction message to the terminal device on a first band, wherein the instruction message comprises the time information and is used to instruct the terminal device to detect information transmitted by the wireless access device on the second band, such that the terminal device starts detecting information transmitted on the second band after the instruction message is received and after the second duration expires; when the information transmitted by the wireless access device on the second band is detected within the first duration, uses the moment at which the information transmitted by the wireless access device is detected as the start moment at which the wireless access device sends information on the second band; and stops detecting information transmitted on the second band and enters a dormant state on the second band, if the terminal device does not receive, within the first duration, information transmitted by the wireless access device on the second band; obtaining permission to use a spectrum resource on the second band; and sending the information transmitted by the wireless access device to the terminal device on the second band. determining time information used to instruct a terminal device to detect information transmitted by the wireless access device to the terminal device on a second band, comprising determining a candidate timeslot corresponding to a time segment in which the information is sent on the second band, wherein the time information includes a first duration and a second duration, the first duration is a duration in which the terminal device detects the information transmitted by the wireless access device on the second band, the second duration is a first time interval between a moment at which the terminal device receives the instruction message and a moment at which the terminal device starts to detect the information transmitted by the wireless access device on the second band, and the second duration is less than or equal to a second time interval between the moment at which the terminal device receives an instruction message and a start moment of the candidate timeslot; sending the instruction message to the terminal device on a first band, wherein the instruction message comprises the time information and is used to instruct the terminal device to detect information transmitted by the wireless access device on the second band, such that the terminal device starts detecting information transmitted on the second band after the instruction message is received and after the second duration expires; when the information transmitted by the wireless access device on the second band is detected within the first duration, uses the moment at which the information transmitted by the wireless access device is detected as the start moment at which the wireless access device sends information on the second band; and stops detecting information transmitted on the second band and enters a dormant state on the second band, if the terminal device does not receive, within the first duration, information transmitted by the wireless access device on the second band; obtaining permission to use a spectrum resource on the second band; and sending the information transmitted by the wireless access device to the terminal device on the second band.