A data transmission method suitable for transmitting a first data table from a server to a mobile device is provided, wherein the first data table has a plurality of first data fields. The data transmission method includes following steps. A maximum used bit number of each of the first data fields is identified, wherein when the maximum used bit number of one of the first data fields is 0, the first data field is deleted so as to form a second data table. The second data table is then transmitted to the mobile device.