In this paper an innovative miniaturized spectrometer has been presented. The structure is similar to a grating spectrometer, but its optical modulator is composed of a grating and a tunable Fabry-Perot (FP). The collimated light is diffracted by the grating and filtered by the FP, and interference fringes distribute separately on the focal plane. The position of fringes moves when the FP is tuned, this helps in the scanning and detecting of the peak wavelength of fringes. The principle and characteristics of the spectrometer are discussed in detail.