Abstract: Mass resolution of a mass spectrometer refers to the ability of the instrument to distinguish between two ions of similar mass, and is an important indicator of the instrument. In order to maintain the stability of the mass resolution of the quadrupole mass spectrometer, reduce the maintenance cost of the instrument, and realize the automation and intelligence of the instrument, the laboratory developed a set of automatic adjustment algorithms for mass resolution of the quadrupole mass spectrometer. The algorithm detected the full width at half maximum (FWHM) of the mass spectrum, and adjusted the instrument by comparing with the set FWHM target value. Through this process the FWHM finally reached the target value and the instrument achieved the purpose of automatic adjustment of mass resolution. This work was based on quadrupole mass spectrometer which was designed by National Institute of Metrology (NIM). Follow the way of this instrument’s circuit designed, the algorithm flow was built, and algorithm theory was putted on this instrument. At last, using the standard material perfluorotributylamine (PFTBA), which was commonly used in quadrupole mass spectrometers, the test algorithm was used to adjust the mass resolution of the quadrupole mass spectrometer. The experimental results were all up to expectations. The algorithm had universal applicability to the quadrupole mass spectrometer, which reduced the requirement for the operator to adjust the instrument and improved the stability of the instrument. After many tests, the algorithm could achieve the purpose of reducing the deviation of experimental data and improving the quality resolution of the spectrum.