A relay protection facility and method based on online fault component impedance measurement are provided. The facility comprises a measuring unit, a feature quantity extracting unit, a comparing unitand an action unit, wherein the measuring unit measures three-phase voltage and three-phase current in a cycle from a busbar and outputs the same to the feature quantity extracting unit; the featurequantity extracting unit outputs the extracted feature quantity to the comparing unit; the comparing unit compares the feature quantity with a setting value, and outputs a determination result to theaction unit; and the action unit, according to the determination result, givens an automatic reclosing command. The facility and method use the fault component impedance obtained based on the online measurement as the feature quantity, and solve the decrease in reliability and selectivity of grid current protection with the offshore wind power base access due to a decrease in short-circuit currentdiscrimination.