This study was performed to investigate the air pollution tolerance of urban trees; Gingko biloba, Platanus occidentalis, Salix pseudolagiogyne and Purunus serrulata growing in Seoul, Taegu, Chungju area. Vitality of trees and water soluble sulfur content in the leaves were determined at 24 points in those cities. The ratio of the each number of Platanus occidentalis, Gingko biloba, Salix psuedolagiogyne and Prunus serrulata to the total number of urban tree in Seoul area was $49.38\%,; 17.36\%,; 13.42\%,;2.43\%$, respectively. Its ratio in Taegu area was $36.76\%,;14.25\%,;13.36\%,;3.32\%$ and in the Chungju area was $59.06\%,;17.35\%,;11.09\%,;8.33\%$, respectively. The species deversity was 0.7017, 09067, 0.5297 in Seoul, Taegu, Chungju, respectively. The significant correlation between the S02 concentration and the tree vitality highly found on Platanus occidentalis, Gingko biloba, Salix pseudolagiogyne and Prunus serrulata. Positive correlation coefficient between $SO_2$ concentration and water soluble sulfur content were shown on Platanus occidentalis, Salix pseudolagiogyne and Prunus serrulata and that between tree vitality and water soluble sulfur content were shown on Platanus occidentalis and Gingko biloba. The tolerant to the S02 gas was high in order of Salix pseudolagiogyne, Gingko biloba, Prunus serrulata and Platanus occidentalis. Also the absorption activity to the $SO_2$ gas was high in order of Salix psuedolagiogyne, Gingko biloba, Platanus occidentalis and Prunus serrulata.