The invention discloses a photonic crystal fiber and a surface plasma resonance sensor. The photonic crystal fiber comprises a magnesium fluoride layer, a silicon layer, a silver wire and a fiber body, wherein the center position of the fiber body is provided with an axial air hole, the silver wire is axially arranged at the center portion of the fiber body, to-be-detected liquid is axially filledinto the fiber body, the to-be-detected liquid is wrapped in the magnesium fluoride layer, the magnesium fluoride layer is arranged at an outer layer of the air hole and the silver wire, and the other space of the fiber body is filled by the silicon layer. The photonic crystal fiber is advantaged in that the magnesium fluoride layer is arranged at the outer layer of the silver wire, so silver oxidation can be effectively prevented, generation of a surface plasma resonance phenomenon is guaranteed, not only can sensitivity and measure precision be improved, but also service life is prolonged.