A data transmission method includes: starting transferring chunks in a first data block of an image file to a device via a Bluetooth network; when a number of at least one first trunk in the chunks that has been transferred to the device equals to a transfer window, determining whether the device receives all of the at least one first trunk to update the chunk missing data; if the device receives all of the at least one first trunk, dynamically adjusting the transfer window according to the chunk missing data to continue transferring remaining chunks in the chunks or a second data block of the image file to the device; and if the device fails to receive all of the at least one first trunk, retransferring at least one chunk that is not previously received by the first device to the device.