Abstract: The Xuanwei City in Yunnan Province is known to have the highest occurrence rates of lung cancer in China. Previous studies have revealed that the lung cancer incidence in this area was associated with indoor coal burning. During January, March and December 2011, indoor and corresponding outdoor PM₁₀ samples were collected from 18families located in different towns in Xuanwei City, and 2families in Xingfu Village of Liupanshui City in Guizhou Province as the control group by Minivol samplers. Morphologies and size distributions of PM₁₀ samples were determined using the field emission scanning electron microscopy (FESEM) and image analysis (IA). According to the morphology, the particles were classified into soot (e.g., chain, fluffy and compact), spherical (e.g., fly ash and tar ball), mineral (e.g., regular and irregular), biological and ultrafine categories. The number-size distributions showed that indoor and outdoor PM₁₀ in Xuanwei City mainly ranged from of 0.1-0.4μm. The volume-size distributions revealed that indoor and outdoor PM₁₀ in Xuanwei City display their major size ranges between 1-10μm. Fine particles dominated by number, while coarse particles riched by volume in the PM₁₀ of Xuanwei City. The particle distributions by number-size and volume-size in Xuanwei City were similar to that in Xingfu Village. There was only one exception that the volume-size distribution of outdoor PM₁₀ in Xuanwei City had a certain difference from that in Xingfu Village. In the Xuanwei City indoor PM₁₀ number percentages of spherical particles and soot were 23.6% and 10.5% respectively, and these values were higher than those in the Xingfu Village with proportions of 11.3% and 7.7% respectively.