Abstract: A grating-type tunable filter comprises a signal input terminal, a signal output terminal, a focusing component and gratings. An input collimator, an output collimator, a first grating, a first reflector, a light beam expanding component, a second grating, a polarization rotating component and a second reflector are arranged along an optical path. Wavelength selection is realized by changing the incident angles of the first grating and the second grating by virtue of the rotatable first reflector, and the first grating is inserted among the input collimator, the output collimator and the first reflector driven by MEMS to carry out pre-dispersion.