According to the characteristics of superimposed multi-wavelength fiber Bragg gratings,present a mathematic model for superimposed multi-wavelength fiber Bragg Gratings. Theoretical analysis is made using Matrix method for four and eight wavelength superimposed fiber Bragg gratings. The theoretical analysis results is agreement well with the experimental results. Also,the numerical simulation of sixteen wavelength superimposed fiber Bragg gratings which wave gap equals 0.8 nm is made firstly. This method is conducive to the design and fabrication of multi-wavelength superimposed fiber Bragg gratings.