As a kind of clean energy, hydrogen has been widely used in industrial field. However, due to its light molecular weight, it is prone to leakage. When volume ratio of hydrogen in the air reaches 4%, there is a danger of explosion. Therefore, detection of hydrogen concentration is very important in practical applications. In view of the above situation, this paper proposes a Fabry-Perot interferometer (FPI) hydrogen sensor based on polydimethylsiloxane (PDMS) filling. By introducing an arrayed waveguide grating (AWG), it can detect hydrogen concentration at multi-point simultaneously. The proposed sensor is formed by fusion splicing a single mode fiber and a hollow core fiber (HCF), filling the HCF with PDMS and covering the outer surface of PDMS with Pt/WO₃. When Pt/WO₃ reacts with hydrogen chemically, released heat increases local temperature of the hydrogen sensor, and the thermal expansion of PDMS results in shortening the length of air cavity inside FPI, which will cause wavelength shift of interference spectrum. By connecting the sensor with the AWG, wavelength shift can be demodulated into light intensity change, so as to achieve simultaneous multi-point hydrogen concentration measurement.