Decreasing of PM_2.5 concentration in the heating season was not significant in Xi’an. This article determined a land use regression (LUR) model and researched the distribution characteristics of PM_2.5 in heating and non-heating seasons in Xi'an. The results showed that: (1) The R² of LUR was larger than 0.9, and the simulation results were better than previous studies. (2) The PM_2.5 concentration in the heating season was larger than in the non-heating season. In Xi’an, the distribution of PM_2.5 concentration was low in the southeast and high in the northwest in the non-heating season and was low in the southeast and high in the main urban region in the heating season. (3) The PM_2.5 concentration was affected by temperature, average air pressure, altitude, humidity and precipitation in non-heating season and was influenced by precipitation, altitude, average air pressure, vegetation, and density of roads in heating season. (4) This paper showed some improvements in selection of potential variables for LUR model, and the conclusion can provide a scientific basis for PM_2.5 pollution control and a reliable method for simulating PM_2.5 concentration in other cities.