To investigate the characteristic of atmospheric ammonia pollution and its influence on the secondary inorganic components of PM_2.5， online measurements of atmospheric ammonia and aerosol components have been conducted in Nanjing， Wuxi， Zhenjiang， Changzhou and Xuzhou of Jiangsu Province， simultaneously from 2021 to 2022， the effect of ammonia emission reduction of Jiangsu province have been evaluated by ISORROPIA model. As a result， the average annual ammonia concentration in five cities was 10.1μg/m³， and the concentration in different cities ranged from 7.7 μg/m³（Nanjing） to 15.2 μg/m³（Xuzhou）. The peak concentration of total ammonia was observed in June in summer. Influenced by temperature and thermal equilibrium of ammonium nitrate， the mass concentration of ammonia peaked at noon， while the ammonium increased at night and decreased during daytime. The five cities are at the ammonia rich level and the aerosol is neutral throughout the year. The potential of ammonia to neutralize extra acidic gas is strong. All the cities in Jiangsu Province can achieve significant reductions of PM_2.5 mass concentrations only through prominent reductions of ammonia emission(more than 60%)， while the reductions of SO₂ and NO_X can mitigate PM_2.5 pollution more efficiently.