Abstract: To investigate the pollution characteristics and source apportionment of PM_2.5 in Shiyan City (an inland mountainous city), ambient PM_2.5 samples were collected simultaneously at four environmental monitoring sites from January 12^th to February 4^th, 2016. Chemical analysis was also conducted for elements, water-soluble inorganic ions, organic carbon (OC) and elemental carbon (EC). Seven kinds of pollution sources, including resuspended dust, bare mountain dust, construction dust, coal combustion source, mobile vehicle exhaust, industry exhaust and residential meat cooking were studied, and the local chemical profiles of the pollution sources in Shiyan City were preliminary established. Statistical methods were used to study the PM_2.5 pollution characteristics in winter in Shiyan City. Source apportionment of PM_2.5 was carried out by using the chemical mass balance (CMB) receptor model and the 'dual source analytical technique'. The average mass concentration of PM_2.5 was around 110.65 μg/m³, which exceeded the level Ⅱ 24-hour limit values of the Ambient Air Quality Standard (NAAQS, GB 3095-2012). The concentration of PM_2.5 increased with the relative humidity. There is no obvious spatial difference of the PM_2.5 mass concentrations and their components among the three urban monitoring sites. The most important components in PM_2.5 were TC, NO₃^- and SO₄^2-, which were closely related to the secondary reactions, mobile vehicle exhausts and coal combustions. The average ρ(NO₃^-)/ρ(SO₄^2-) value was 1.22, indicating that the contribution of mobile sources was more important. The secondary transformation, coal combustion and mobile vehicle emissions were identified as the most important sources for PM_2.5, with 51.2%, 10.9% and 10.1% respectively. The results showed that the PM_2.5 mass concentrations in winter in Shiyan City exceeded the level Ⅱ 24-hour limit values of NAAQS and the pollution control of PM_2.5 should be focused on multiple sources, such as secondary transformation, coal combustion and mobile vehicle emissions.