This application provides an uplink transmission method, a terminal, and a network side device. The method includes: storing, by a terminal, an uplink transmission time-frequency resource allocated by a network side device; when the terminal needs to send an uplink signal, determining the to-be-transmitted uplink signal based on a quantity of orthogonal frequency division multiplexing (OFDM) symbols in the uplink transmission time-frequency resource; and sending, by the terminal, the uplink signal to the network side device. During implementation of the uplink transmission method provided in this application, grant free transmission solutions are provided for different uplink transmission time-frequency resources, to effectively improve communication performance.