Abstract: In order to focus on the main emission sources, decrease control cost, make pollution control more efficient during winter air pollution control campaign organized by the government of Lanzhou City, 10 samples were collected for SEM analysis at 8 sampling sites in Lanzhou City during December 21-23, 2011. The results showed that individual particles in Lanzhou City could be divided into several groups: irregular particles, chain particles, round particles, crystal particles and multi-source-particle mixture. Typical particles of grape-like particles and liquid surface particles were found at Yuzhong Industry Park and Xigu District. The PM sources in Lanzhou City included mainly fugitive dust, coal burning, vehicle emission and secondary particles. Though vehicle emission particles could be found at all sites in Lanzhou City, they were not the important sources at most sites. Particles from Yuzhong Industry Park and Xigu District probably had obvious effect on the air quality of downtown Lanzhou. The particles of downtown Lanzhou mostly came from local sources. It was suggested that fugitive dust and coal burning should be controlled strictly in downtown Lanzhou, and industry emission be controlled tightly at Yuzhong Industry Park and Xigu District.