Measurements of sulfur dioxide, ozone and meteorological parameters at Kosan, Cheju Island show clear indications of the influence of the source areas of both Korean Peninsular and Mainland China. Monthly mean levels in February of $SO_2$ and $O_3$ were 1.4 and 44 ppb, respectively. These Values are 2-30 times higher than those measured in remote are as such as Bermuda Island and Uto Island in Finland. Ozone loss in February and March were found to be 0.2 and 0.36 ppb/hr and correlation coefficient between ozone and solar radiation was 0.48. Also it was found that $SO_2$ levels were more than 2 times higher when the prevailing winds from WSW-NNE than from the rest.