Example communication message sending methods and apparatus based on backoff duration are described. One example method includes that a terminal device sends an access request to a cell to which the terminal device belongs. The terminal device monitors a downlink control channel, and receives an access response message based on scheduling information on the downlink control channel. If the access response message carries a backoff access identifier, the terminal device determines a backoff parameter corresponding to the backoff access identifier in the access response message based on a correspondence that is pre-stored and that is between the backoff access identifier and the backoff parameter. The terminal device determines backoff duration based on the backoff parameter and an access resource interval period corresponding to the terminal device, and sends an access request to the cell after the backoff duration.