Data transmission methods and devices are provided. A data sender determines a target sending position based on channel detection results of available sending positions within a set time window. The length of the set time window is associated with a type of data to be transmitted. The data to be transmitted includes signaling or a signal that is periodically sent. The length of the set time window does not exceed a transmission period of the data to be transmitted. The data sender may further transmit the data at the target sending position.