A data transmission system is utilized in a Mobile Industry Processor Interface (MIPI). A master device includes a control module for generating a control signal according to a feedback signal. A packet encoding module is coupled to the control module for encoding an original packet to be a transmission packet according to the original packet and the control signal to process a transmission operation. A slave device includes a packet decoding module for decoding the transmission packet to be the original packet or a related display device signal corresponding to the original packet to a display device. A feedback module is coupled to the packet decoding module for generating the feedback signal to the control module of the master device according to a decoding condition of the control module, so as to switch a transmission mode of the transmission operation.