Provided are an electric power steering system and a method for checking an initial driving thereof, in which no additional redischarging and charging time is required by simultaneously determining a freezing of a safety switch and/or a safety switch off of a sub MCU, which monitors a state of a main MCU, thereby shortening initial driving time of the electric power steering system. The electric power steering system includes: a power supply; a motor configured to generate steering auxiliary power; a safety switch provided between the power supply and the motor and configured to control supply of power; a main MCU configured to control an operation of the safety switch; and a sub MCU configured to monitor a state of the main MCU. The main MCU applies an on driving signal to the safety switch, receives front and rear stage voltages of the safety switch, and determines that the safety switch has been frozen and/or a safety switch off function of the sub MCU has failed, when there is no potential difference between the received front and rear stage voltages.