Abstract: This paper studied the aeroanion concentration in Shenyang EXPO Park. According to observation，conclusions are the following：(1)The air in the park is very clean and the aeroanion concentration is twice the residential areas in urban. (2)It was showed that the aeroanion concentration changed obviously during a day. The concentration was higher in early morning and midnight, and the ability of air was better. In mid-day, the air-anion concentration was lower. (3)The aero-anion concentration was obvious difference in different environment of recreation. By the aero-anion concentration, the descending order is follows: waterside, forests, woodside square, spacious lawn, greenhouse. (4)There was obvious negative correlation between aeroanion concentration and temperature and obvious positive correlation between aeroanion concentration and humidity of air.