The invention provides an optical fiber inhaul cable prestress monitoring method and a sensor of the optical fiber inhaul cable prestress monitoring method. According to the prestress monitoring method, a single-mode optical fiber wound around the outer surface of a prestress monitored part serves as a sensing unit, and long-term and stable monitoring of the prestress is achieved. The sensor of the optical fiber bridge inhaul cable prestress monitoring method comprises a prestress monitoring module, a temperature compensation module, a signal transmission segment optical cable and a protecting steel sleeve. The prestress monitored part is used for monitoring the stress on a prestressed anchorage device stressed part, and then the prestress on an inhaul cable is obtained. An optical fiber coil wound around a temperature compensation monitored part is used for correcting influence on the prestress monitoring result from environment temperature, so that strain monitoring is more accurate, and meanwhile measurement of the interior temperature of a cable body is achieved, wherein the temperature compensation monitored part is of the same specification as the prestress monitored part, is not stressed and is located in the same temperature environment as the prestress monitored part. The method is suitable for long-term monitoring of the prestress on the bridge inhaul cable and has the advantages that precision is high, the service life of the sensor is long and the cost is low.