Arsenic (As) is a ubiquitous carcinogen in the environment. Its bio-toxicity is significantly correlated with its chemical forms. In this study, As accumulation and speciation of PM_2.5 was investigated in Jinan. The high PM_2.5 levels fluctuated between 69.67 μg·m^-3 and 211.25 μg·m^-3 in winter, and ranged from 63.46 μg·m^-3 to 125.50 μg·m^-3 in summer. The total As concentration of PM_2.5 in winter and summer varied from 4.23 to 15.47 ng·m^-3 and from 4.59 to 11.69 ng·m^-3. As(V) accounted for 70~100% of the extractable speciation in the PM_2.5 samples. Exposure levels of total As for the general public were 63.45~232.05 ng d^-1, and 68.85~175.35 ng d^-1 by inhalation in winter and summer. The mean of cancer risk (CR) of As in PM_2.5 for winter and summer were 7.30×10^-6±0.89×10^-6 and 5.26×10^-6±0.58×10^-6, respectively.