The performances of the monopole mass spectrometer were analyzed that it had high resolving power and focusing property. The monopole mass spectrometer whose electrode length was 100mm and r0=5mm had been designed and manufactured. The resolving power and mass range of it had been measured. The researching results indicated: The mass range of the device was 223. The resolving power achieved 30 measured at 10% peak height of the N2^+. The device could he used in residual gas analysis.
