The spatial and seasonal variation characteristics are discussed by using the data at three monitoring stations from 1993 to 2006 in Beijing and Tianjin. The MannKendall trend test was applied to examine the trend of ac id rain in recent 14 years．The results show that three stations have some resem bling characteristics, such as high level of pH value in autumn and winter，lo w lev el of pH value in spring and summer. However， the changing trend of three stati ons is very different. The acid rain frequency at Tianjin Station is serious at the beginning of the 1990s， but the state of acid rain has improved obviously recently. On the other hand, the value of MK method in Changping Station is -3.17，[JP2] indicating t hat the state of acid rain has deteriorated obviously[JP] during the last 14 years. As the suburb of Beijing， Shangdianzi Station was improved before 2002, but afterwards the state of acid rain has become increa singly serious.