Embodiments of this application provide a data transmission method and apparatus. The data transmission method is applied to a network based on a CSMA/CA mechanism and the network includes a plurality of nodes that share one channel. According to the data transmission method, a sending node determines, in the plurality of nodes through a first clear channel assessment, that the channel is idle. The sending node then waits for a delay duration, and performs a second clear channel assessment on the channel after the delay duration. The sending node sends a data frame to a receiving node in the plurality of nodes through the channel in response to determining, through the second clear channel assessment, that the channel is idle. The sending node performs a clear channel assessment twice before sending a data frame, which reflects priorities of different types of data frames and shortens a network latency.