A transmitting system and a method of transmitting digital broadcast signal are disclosed. The method of transmitting digital broadcast signal includes generating signaling data including a transmission parameter, wherein the transmission parameter includes a protocol version field identifying between a first transmission mode and a second transmission mode, forming a data group including mobile service data and the signaling data, forming mobile service data packets including the mobile service data and the signaling data in the data group, transmitting the digital broadcast signal including the data group.