The invention provides a novel hydrogen-sensitive thin film-based optical fiber hydrogen detection system. A light signal output by a wavelength-adjustable laser source is input through one of two ends of an optical fiber branching device, and then is transmitted to a sensing probe from the single end of the optical fiber branching device; returned light is transmitted to a photoelectric detectorfrom the other end of the two ends of the optical fiber branching device, and then is converted into a hydrogen concentration and a working temperature of a novel hydrogen-sensitive thin film in a data display and processing system for displaying; a control system controls the output power of a heating light source so as to heat the sensing probe; the sensing probe comprises a multi-hole heat conduction cavity; two single-mode optical fibers are arranged in the multi-hole heat conduction cavity; a reference grating and a temperature measurement grating are arranged on one single-mode optical fiber connected with the optical fiber branching device; the hydrogen-sensitive thin film is deposited at the end part; the other single-mode optical fiber is connected with the heating light source; the end part of the multi-hole heat conduction cavity is sealed by epoxy resin. By the adoption of the hydrogen-sensitive thin film, the probe structure and a signal processing method, on the premise of guaranteeing high precision, the cost is reduced.