The problem of environmental pollution was troubling people in many cities in China, especially PM_2.5 pollution. Aiming to a better understanding the influence of long-range transport sources and health effect of PM_2.5 in Ji'nan, a field observation was carried out in from 23 December 2016 to 25 April 2017. The results showed that primary organic carbon (POC), secondary organic carbon (SOC) and element carbon (EC) during observation in Ji'nan were 5.45, 2.59 and 2.76 μg m⁻³, respectively. In heavy pollution days, OC and EC likely had similar primary emission and transmission sources. While the contribution of SOC increased in PM_2.5 in clear days. Based on the potential source contribution function (PSCF) analysis, the emission sources leading to aggravation of PM_2.5 pollution in Ji'nan were mainly distributed in the surrounding area of Ji'nan, especially in the eastern and southeastern Shandong. The risk assessment results show that the premature death caused by PM_2.5 pollution could reach 666 people, and about 1.47% of total annual deaths in Ji'nan in 2016. The medical consumption related to PM_2.5 pollution was about 202 millions USD, accounting for 2.05‰ of the GDP in Ji'nan in 2016. Lung-cancer mortality caused the highest economic cost of 47.97 millions USD, followed by respiratory mortality, chronic bronchitis, cardiovascular mortality, and acute bronchitis.