A communication message sending method, wherein the method comprises: sending, by a terminal device, a communication message to a cell to which the terminal device belongs; if the terminal device does not receive, in preset duration after the communication message is sent, a response message sent by the cell, or the terminal device receives a response message that carries a backoff transmission identifier and that is sent by the cell, obtaining, by the terminal device, a backoff parameter, and determining, based on the backoff parameter and a basic backoff timeslot corresponding to the terminal device, backoff duration; and re-sending, by the terminal device, an access request to the cell after the backoff duration; wherein before the determining, based on the backoff parameter and a basic backoff timeslot corresponding to the terminal device, backoff duration, the method further comprises: determining, by the terminal device based on a correspondence that is pre-stored and that is between each channel and the basic backoff timeslot, a basic backoff timeslot corresponding to a to-be-used first channel; wherein the basic backoff timeslot indicates a minimum duration unit when the terminal device performs backoff; and correspondence information between each channel and a modulation and coding scheme, MCS, and a backoff parameter on each channel is comprised in a system message, and is sent by the cell to the terminal device, wherein the backoff parameter is a multiple of the basic backoff timeslot. sending, by a terminal device, a communication message to a cell to which the terminal device belongs; if the terminal device does not receive, in preset duration after the communication message is sent, a response message sent by the cell, or the terminal device receives a response message that carries a backoff transmission identifier and that is sent by the cell, obtaining, by the terminal device, a backoff parameter, and determining, based on the backoff parameter and a basic backoff timeslot corresponding to the terminal device, backoff duration; and re-sending, by the terminal device, an access request to the cell after the backoff duration; wherein before the determining, based on the backoff parameter and a basic backoff timeslot corresponding to the terminal device, backoff duration, the method further comprises: determining, by the terminal device based on a correspondence that is pre-stored and that is between each channel and the basic backoff timeslot, a basic backoff timeslot corresponding to a to-be-used first channel; wherein the basic backoff timeslot indicates a minimum duration unit when the terminal device performs backoff; and correspondence information between each channel and a modulation and coding scheme, MCS, and a backoff parameter on each channel is comprised in a system message, and is sent by the cell to the terminal device, wherein the backoff parameter is a multiple of the basic backoff timeslot. determining, by the terminal device based on a correspondence that is pre-stored and that is between each channel and the basic backoff timeslot, a basic backoff timeslot corresponding to a to-be-used first channel; wherein the basic backoff timeslot indicates a minimum duration unit when the terminal device performs backoff; and correspondence information between each channel and a modulation and coding scheme, MCS, and a backoff parameter on each channel is comprised in a system message, and is sent by the cell to the terminal device, wherein the backoff parameter is a multiple of the basic backoff timeslot.