Abstract:From June 2007 to November 2008, the throughfalls of masson pine and mixed wood was collected and measured at Longli experimental plot in Guizhou province. The acidity and chemical composition of throughfalls were analyzed with statistical methods to reveal the leach characteristics and seasonal tendency of local acid rain. pH values of precipitation increased obviously after getting through the crowns, and mixed wood had a better cushioning effect against acid rain than masson pine. Under the action of acid deposition in the perennial, crowns of masson pine and mixed wood had a certain absorption of NH4+ and NO3-, which could mitigate local soil’s acidification. Acid rain induced nutrient ions such as Mg2+, K+ and Ca2+ to leach and lose.