On the basis of the properties of red soils and the features of acid rain the characteristics of sensitivity of red soils to acid rain in South China are dealt in the present article. An acid-buffer curve method is put forward for studying the sensitivity of red soils to acid rain. In terms of soil acid-buffer curves two indices, i.e, soil acid-damage capacity and soil acid-sensitivity value (△pH s.v.), are proposed. According, to a lot of results of acid-buffer curves the primary classes of both indices and the reconnaissance division map of soil acid-sensitivity in Guangdong, Guangxi and Hainan have been made.