Abstract: The miniature sector Mass Spectrometer has been deployed for many real-time in-situ analysis applications due to its simplicity,high sensitivity,small size,low power consumption,stability and suitability to harsh environments.The three types of sector Mass Spectrometers are described and their development and applications are introduced.Those are signal-focusing magnetic sector Mass Spectrometers,tandem field double-focusing sector Mass Spectrometer and crossed electric and magnetic fields or E×B superimposed field sdouble-focusing sector Mass Spectrometer.Micro-electromechanical Systems(MEMS)applied to Mass Spectrometer are noted and the possible future development of miniature Mass Spectrometer is analyzed.