In this paper,the environmental meteorological stations in Xi'an are classified into urban,suburban,and two types of rural stations based on the proportion of construction land and the information entropy of land use.Following that,the urban-rural distribution characteristics of PM_2.5 are then explored,as well as the correlation between the urban-rural PM_2.5 concentration difference and the urban heat island effect intensity (UHII).Results show that the urban-rural distribution characteristics and the diurnal variation characteristics of PM_2.5 in Xi'an vary with the season.The PM_2.5 concentrations of the two types of rural stations are significantly different.Evidently,the correlation coefficients between UHII_D and PM_2.5 concentration of urban (rural D) stations are higher than those between UHII_U and PM_2.5 concentration of urban (rural U) stations.Furthermore,because of more emissions,the correlation coefficients between UHII_U (UHII_D) and PM_2.5 concentration of rural stations are greater than those between UHII_U (UHII_D) and PM_2.5 concentration of urban stations.UHII_D-RUPII_D demonstrates a negative correlation in the spring,summer and autumn as UHII_D increases,with the relative urban-rural PM_2.5 concentration difference (RUPII_D) showing a downward trend.In addition,the urban area's vertical diffusion capacity of PM_2.5 is greater than its horizontal diffusion capacity the larger the UHII_D.By changing the transmission and diffusion characteristics of PM_2.5,UHII_D further influences RUPII_D in Xi'an.