Abstract: Using the 16 years' pH values of precipitation to analyze the changing characteristics of year,season and month in Jishou during 1992-2007 and comparing with meteorology data in the same period,the results showed that annual pH values of precipitation in Jishou,as the year goes on,the situation of bias acid precipitation had not improved obviously.pH values of precipitation were low and the frequency of acid rain was high in winter and spring.pH values of precipitation had clearly relations with the cloudy days,wind speed,rainfall intensity,rainfall duration,terrain and urban development.Some measures,such as,industry desulfurization,dustfall and energy saving and emission reduction were proposed to increase the pH values of precipitation and reduce the impacts of acid rain.The results could provide a reference to improving the air quality of the city and the living environment.

Key words: pH values of precipitation, Change characteristics, Causes of acid rain