The invention provides a frequency converter overload protection system, which comprises an output control unit, a torque calculation unit, an output detection unit and an overload protection unit. The output control unit is used for making the frequency converter reach a set operation frequency and operate at the set frequency for specified time when the frequency converter executes a lifting operation; the output detection unit is used for detecting the output voltage and current of the frequency converter; the torque calculation unit is used for calculating the output torque of the frequency converter according to the output voltage and current; and the overload protection unit is used for determining overload and making the frequency converter execute deceleration and stop operations when the output torque exceeds a set maximum output torque, while disabling the lifting command. The invention also provides a corresponding method. According to the invention, frequency converter overload is determined by detecting the torque in uniform speed operation of the frequency converter, to achieve high overload determination accuracy and low cost.