This Portable Mass Spectrometer is light. The overall weight is about 20Kg with the size of 33 x 40 x 28 cm. It can be used to measure very broad mass range; from atom to microparticle such as cell. Mass resolution is unit mass at low mass region. For illegal drug detection such as Methamphetamine and MDMA, it can reach 10 ng/ml. For detection of pollutants in air, sensitivity can reach ppbv. pMS has a feature to achieve collision induced dissociation to obtain MS(2) and MS(3) that can enhance specificity dramatically. Main applications include (1) biomedical research such as biomarker detection (2) disease diagnosis (3) food and drug purity detection (4) material identification (5) detection of the masses of nanoparticles, microparticles, virus and cells and (6) air pollutant and water pollutant detection.