A MEMS-based pitch-tunable grating with continuously variable pitch is proposed.The grating is electrostatic comb actuated.With the change of the voltage,the pitch and the diffraction angle of specific order are also changed simultaneously.In order to supervise the change of diffraction angle,an experimental measurement system is designed and established,the diffraction angle′s variability is obtained by image processing.The measured results agree with the theoretical calculation very well.The error has resulted from image processing and structure machining technics error.The experimental results testify about the tuning range of pitch(5%) adequately.This work lays a good foundation for our future research in micro spectrometer and optical communication,and provides valuable technical references.