An advanced particle microphysics (APM) model has been incorporated into a regional chemical transport model, NAQPMS, to simulate the seasonal variation of particle number concentrations over China in 2007 for the first time. The NAQPMS+APM can reproduce the particles number concentrations at remote, suburban sites and urban sites reasonably. Most of modeled values were within a factor of two of observations. The simulation indicated that particles number concentration was significantly higher in southeastern China than that in northwestern China. Monthly mean number concentration can be over 20000 cm^-3 in most polluted regions in southeastern China while the value is generally below 7000 cm^-3 in northwestern parts of China. Higher number concentration occurred in January while lower value occurred in April and July. In heavily polluted regions, like Sichuan Basin and central-eastern China, primary particles dominated particles number, while secondary particles formed via the nucleation process account for most of particles number over relative clean areas. The area over which secondary particles dominated showed distinct seasonal variation and its spatial pattern was coupled with primary particles distribution which was strongly influenced by the meteorological conditions, e.g., East Asia Monsoon.