Europe has already established tentative critical levels of air pollutants based on the dose responses. Current ozone level has the potential adverse impact to plants. However, the relation with air pollutants is not clarified. The purpose of this study make GIS database to evaluate the relationship between air pollutants and forest decline, quantitatively and visually, and proposes critical level mapping method. The observation data, such as the forest decline monitoring data, the long term monitoring data of air pollutants and the meteorology data was collected. Geostatistical analysis (kriging method) was applied for making oxidant based accumulated exposure Over a Threshold of 40 ppb (A0T40) map from 1975 to 2001. And, the relation between air pollutants and Red pine, Larch, and Beech forest decline was analyzed using GIS database. Trials to present excess maps of pollutants would help a risk assessment of the impacts on forests health using critical levels evaluated by exposure experiments. AOT40 seemed to be effective as an index of the vegetation influence evaluation.