The inherent cross sensitivity of optical fiber sensor is always an urgent problem to be solved in the application of optical fiber sensing technology. A multi-objective particle swarm optimization(MPSO) demodulation algorithm is proposed. The demodulation of two fiber Bragg grating(FBG) central wavelengths in the same and different sensing systems is discussed respectively, and the influence of different reflectivity on the demodulation results is also discussed. This method not only has high detection accuracy, the temperature measurement accuracy is 0.1 ℃, the strain accuracy is 0.5 με, but also the system structure is simple and easy to realize, which has no strict restrictions on the material, structure, central wavelength and reflectivity of FBG.