A channel listening method applied to an unlicensed frequency band, wherein the method comprises: performing, by a communications device (101, 900, 1000, 1021, 1022, 1023), clear channel assessment on a first beam, and in a process of the clear channel assessment, performing, by the communications device (101, 900, 1000, 1021, 1022, 1023), a backoff in terms of time based on a backoff control parameter for the first beam, wherein the communications device (101, 900, 1000, 1021, 1022, 1023) has a plurality of optional beams, the first beam is one of the plurality of optional beams, and the backoff control parameter is set based on a historical value of a backoff control parameter for at least one of the plurality of optional beams, wherein the backoff control parameter is set based on a historical value of a backoff control parameter for a beam that is in the plurality of optional beams and that is associated with the first beam or a historical value of the backoff control parameter for the first beam, the beam associated with the first beam being associated with the first beam based on spatial ranges covered by the beams, and if neither the backoff control parameter for the beam associated with the first beam nor the backoff control parameter for the first beam has a historical value, the backoff control parameter is set based on a preset upper limit, the preset upper limit being set based on historical values of backoff control parameters for the plurality of optional beams or quantities of times of backoff interruption on the plurality of optional beams; and after the backoff succeeds, performing, by the communications device (101, 900, 1000, 1021, 1022, 1023), transmission by using the first beam. performing, by a communications device (101, 900, 1000, 1021, 1022, 1023), clear channel assessment on a first beam, and in a process of the clear channel assessment, performing, by the communications device (101, 900, 1000, 1021, 1022, 1023), a backoff in terms of time based on a backoff control parameter for the first beam, wherein the communications device (101, 900, 1000, 1021, 1022, 1023) has a plurality of optional beams, the first beam is one of the plurality of optional beams, and the backoff control parameter is set based on a historical value of a backoff control parameter for at least one of the plurality of optional beams, wherein the backoff control parameter is set based on a historical value of a backoff control parameter for a beam that is in the plurality of optional beams and that is associated with the first beam or a historical value of the backoff control parameter for the first beam, the beam associated with the first beam being associated with the first beam based on spatial ranges covered by the beams, and if neither the backoff control parameter for the beam associated with the first beam nor the backoff control parameter for the first beam has a historical value, the backoff control parameter is set based on a preset upper limit, the preset upper limit being set based on historical values of backoff control parameters for the plurality of optional beams or quantities of times of backoff interruption on the plurality of optional beams; and after the backoff succeeds, performing, by the communications device (101, 900, 1000, 1021, 1022, 1023), transmission by using the first beam.