In industrial fields,there are important applications of ultra high purity（UHP） gas,which surely need the technical support with high sensitivity detection methods of trace impurities.For this challenge,the most effective technique is atmospheric pressure ionization mass spectrometry（APIMS） with high sensitivity 104-106 times higher than that of conventional electron impact mass spectrometry（EIMS）.In this article,the emergence,development and ionization principle of APIMS were introduced.Also,the previous research work in analysis of UHP gas by APIMS was reviewed.The specific contents for variety of matrix and impurity gases,the impurity detection limit and the detection method for specific impurities were included.The detection limits of the impurities were more emphasized in this article as the sensitivity is a key point to the purity analysis on UHP gas.