Disclosed herein are an electronic parking brake system and a control method thereof. The electronic parking brake system includes a parking brake apparatus with a parking cable, a force sensing unit to sense tension of the parking cable, and an electronic control unit to measure braking force of the parking brake apparatus based on the tension, to estimate braking force of a fuzzy model, and to judge malfunction of the parking brake apparatus based on the measured braking force and the estimated braking force. Tension is estimated using the fuzzy model and is compared with the measured braking force, thereby effectively detecting malfunction of the electronic parking brake system and thus raising stability and safety of a vehicle. Further, if a residual exceeds a reference value, it is judged that the electronic parking brake apparatus malfunctions and a warning is given to a driver, thereby preventing accidents.