The present invention relates to a system for coping with a malfunction of an ethanol sensor of a FFV. The present invention provides a system for coping with a malfunction of an ethanol sensor of a FFV, the system including: a driving condition detector configured to determine whether a driving condition of the FFV is satisfied; an air-fuel ratio control condition detector configured to determine whether an air-fuel ratio control condition is satisfied; a timer unit configured to calculate a timer value by measuring time when an ethanol content value measured in the ethanol sensor is constant and when the driving condition and the air-fuel ratio control condition are satisfied; and a controller configured to synchronize an ethanol-content learned value with the ethanol content value measured in the ethanol sensor when it is determined that the timer value calculated in the timer unit is higher than a preset critical value.