The present invention provided a system for transmitting single carrier and a transmitting method thereof. The system for transmitting single carrier comprises: a scrambler randomizes transmitting data signals TS; an FEC(Forward Error Correction) unit corrects a bit error of an inputted randomized data signals TS from the scrambler to form the coding TS; a PN(Pseudo Noise sequence) information generator generates PN information; a Walsh code generator generates a Walsh code corresponding to the discriminating information; a logic combination unit logically combines the generated Walsh code with the PN information; a multiplexer (MUX) is performed by inserting the coding TS into the combined signal by the logic combination unit and the segment synchronous code; a guide frequency inserting unit for inserting the guide frequency to the TS of the multiplexer; a modulating unit for modulating the TS of the inserted guide frequency; and a radio switch for performing the radio switch for themodulated TS from the modulating unit. The system for transmitting single carrier inserts additional information by using a Walsh code, thereby increasing the reliability of transmission signals.