Abstract: An atmospheric pressure interface-quadrupole mass spectrometer was developed. It used a three-chamber vacuum system, which the first vacuum interface was designed based a heated stainless steel capillary, and used a square quadrupole ion guide to transmit ions in the second stage vacuum, used a quadrupole mass filter and a multiplier to analyze and detect ions in the third stage vacuum, and used the home-built control system. Used the instrument, realized the detection of ions generated through the electrospray and dielectric barrier discharge ionization in the atmospheric environment, and daughter ions through the in-source collision-induced dissociation in the first vacuum chamber which improved the qualitative performance. The instrument is simple and low cost, can be used to LC/MS and in-situ analysis.