An　integrated　MM5,　Models-3/CMAQ　modeling　system　was　applied　to　study　SO2　air　quality　in　Beijing　and　its　surrounding　regions　by　the　effects　of　power　plant　emissions　from　Hebei,　Tianjin,　Shanxi　and　Inner　mongolia.　The　result　of　simulation　indicated　that　high　SO2　concentration　was　appeared　in　regions　with　high　density　of　power　plants　and　high　emissions　magnitude.　SO2　concentration　in　Beijing　was　decreased　from　south　to　north,　with　monthly　concentration　of　7.63　and　7.13　μg/m3　in　January,　monthly　concentration　of　5.54　and　5.37　μg/m3　in　April,　monthly　concentration　of　3.02,　3.68　μg/m3　in　July,　monthly　concentration　of　7.49,　7.53　μg/m3　in　October,　and　annual　concentration　of　5.92　and　5.93　μg/m3　in　2005,　for　urban　and　entire　city　of　Beijing,　respectively.　The　maximal　daily　concentrations　of　urban　and　entire　city　of　Beijing　were　30.1　and　19.1　μg/m3　in　January,　which　were　20.1%　and　12.7%　of　the　class　II　national　air　quality　standard.　Power　plant　emissions　in　north　China　induce　or　enhance　air　pollution　in　Beijing,　which　should　not　be　neglected.