Abstract: The change of acid rain in Chongqing city since recent 15 years was analyzed by using linear regression.The results showed that the pH value was relatively low, the annual average pH value in recent 15 years was between 3.8 and 4.5.In recent 5 years of monthly change, the pH value was higher in summer and lower in winner, while the acid rain frequency was lower in summer and higher in winner.The annual pH value increased at a tendency of 0.23/10a.The pH value in autumn increased with fluctuation, while the pH value in the other three seasons didn't have obvious increase or decrease tendency.Acid rain (pH<5.6) frequency in Chongqing was high.It was almost all higher than 80% in each season.The frequency of annual precipitation that pH value lover than 5.6 increased with fluctuate.Acid rain frequency in spring increased obviously and the other three seasons had no obvious trend.The frequency of acid rain exceed relatively strong intensity (pH<4.5) had greatly annual change, which was mainly between 30% and 80%.The annual precipitation that of the pH value was lower than 4.5 fluctuated greatly and had no obvious trend.The acid rain change of Chongqing was mainly influenced by pollutant emission.