Abstract: In order to explore the impact of meteorological factors on PM_2.5 concentration,Xi’an is selected as the research area.Based on the data of air quality and meteorological factors in Xi'an from 2017 to 2019,the K-Means clustering algorithm is improved to form four PM_2.5 concentration and meteorological factor sample clusters of severe pollution,heavy pollution,moderate pollution,light pollution.The distribution of cluster data is analyzed and spearman correlation analysis method is selected to determine the meteorological factors affecting PM_2.5 concentration; the salience condition of PM_2.5 is defined,the amplitude feature FOA (Feature of Amplitude),floating feature FOF (Feature of Float) and salient feature FOH (Feature of Highlight) are given,and the three-dimensional space is constructed to determine the impact of meteorological factors on PM_2.5 concentration,and then the analysis method of the influence of meteorological factors on PM_2.5 concentration is constructed.Compared with multiple linear regression model and random forest regression,the experimental results show that this method simplifies the analysis and calculation process,avoid factor selection and expression,and can effectively determine the influence of meteorological factors and their magnitudes on PM_2.5 concentration.Through this method,under the meteorological conditions of low temperature,high humidity,high pressure and relatively quiet wind,the difficult diffusion and transportation of particulate matter in the air is obtained,so that the PM_2.5 concentration is increased in Xi'an.In severe pollution,heavy pollution and moderate pollution,PM_2.5 concentration is significantly positively correlated with relative humidity,and significantly negatively correlated with wind speed and temperature,and the order of influence is relative humidity>wind speed>temperature.In light pollution,PM_2.5 concentration is significantly positively correlated with relative humidity and air pressure,and significantly negatively correlated with wind speed and temperature,and the order of influence is temperature> relative humidity > air pressure > wind speed.