Abstract In order to evaluate the effectiveness of the PM2.5 emisson control measures for domestic sources, emission sensitivity analysis for seasonal trends and the high concentrations of SO42- in PM2.5, observed in 2010 at Meisei University located in western Tokyo, was implemented based on WRF/CMAQ simulation. The sensitivity was estimated for the emission from volcano, ship, domestic land-based and foreign sources. The sensitivity of foreign emission sources was highest (50.7%) on annual average at the observation site where the local emission strength was relatively small. Especially, it was suggested that the foreign emission sources had a larger contribution to the variation of SO42- concentration during the period of January to April and November to December of 2010. On the other hand, the contribution of foreign emission sources to the high concentration of SO42- decreased during the summer season because of the southern wind from the Pacific High. Since the contribution of both domestic land-based and the ship emission sources was estimated as 41.5% in August 2010, it seemed that the countermeasures implemented for the domestic emissions in summer season was effective in achieving the environmental standard in western Tokyo.