The present invention discloses a data transmission method, apparatus, and system, and an access point. The method includes: transceiving data of a data portion in an uplink OFDMA PPDU scheduled by an access point AP on a corresponding allocated frequency resource unit RU, determining one or more fundamental channel units on which the allocated frequency resource unit RU is located, and transceiving at least some fields in a common signaling portion in the uplink OFDMA PPDU on the determined one or more fundamental channels. In this way, one or more fundamental channels for transceiving at least some fields in a common signaling portion in an uplink OFDMA PPDU are determinate, and another user can transceive data on another idle fundamental channel, thereby improving channel utilization. In addition, multiple users can simultaneously transceive data on multiple fundamental channels, thereby improving a service transmission rate.