The theoretical model of a dual wavelength phase-shifted fiber Bragg grating was established and its spectral characteristics were obtained by numerical simulations, which pointed that the transmission peaks spacing was affected by the amount of phase shift, refractive index modulation and grating length. The expression of transmission peaks spacing was acquired by resonance phase conditions of fiber bragg grating Fabry-Perot cavity, and the curves obtained by numerical simulation method accord well with the curves obtained by analytic formula, proves the correctness of the numerical simulation results. Finally, a sensing method based on transmission peaks spacing of a dual wavelength phase-shifted fiber Bragg grating was proposed, the temperature sensing characteristics were analyzed, and the theoretical sensitivity was about 60 pm/℃.