In order to stably and accurately detect the hydrogen concentration in a high-temperature and high-humidity environment, we proposed a new fabrication method of fiber Bragg grating (FBG) hydrogen sensors in this paper. Firstly, a polydopamine coating, assembled on the surface of FBG by auto-polymerization, was used to adsorb the palladium ions in the palladium chloride solution and form palladium seeds, thus enhancing the adhesion of the palladium seeds on the fiber surface. Secondly, a reducing agent was used to provide a reduction site for the palladium ions so that the palladium seeds were grown into a dense palladium film. Thirdly, a layer of SiO₂ superhydrophobic film was coated on the surface of the palladium film to enhance its stability in a high-humidity environment. Finally, a temperature compensation unit was introduced to eliminate the influence of temperature on the measurement of hydrogen concentration. Furthermore, the effects of polydopamine thickness, the type of the reducing agent, the thickness of the palladium film, temperature, and humidity on the hydrogen-sensitive response characteristics of the sensor were experimentally studied. It is found that the sensor can respond stably and accurately to the changes in hydrogen concentration at the temperature of 30-70 ℃ and the relative humidity of 20%-90%, with a sensitivity of 10.80 pm/% and a relative error of less than 7.2%.