An data transmission adjustment system that comprises a server and a plurality of data transmission devices within a sensing region. The server adapts to receive a sensed data from at least one data transmission device, define a timeline, divide the timeline into a plurality of monitoring periods, calculate a ratio of the number of the monitoring periods that have received the sensing data from the data transmission device within the sensing region or not to the number of all the monitoring periods, and broadcast at least one message to the data transmission devices within the sensing region according to said ratio.