The atmospheric aerosol is measured with optical particle counter at Hefei, Yuexi, Xiamen and Beijing from November 1998 to June 2010 in order to study the aerosol size distribution in typical areas of eastern China, and to establish the aerosol size distribution model. The lognormal distribution is used to fit the size distribution to analyze and compare the size distribution of different months and areas. At last, the aerosol size distribution model of typical areas of eastern China is established.