Background: Asthma is typical allergic disease and incidence rate is increasing. Some cause of increase may be due to pollen change related with climate change. However, in South Korea, a few studies have been performed to explain the correlation of climates changes, pollen count, and allergic diseases using national data such as National Health Insurance Corporation. Objective: The aim of this ecological study was to characterize the correlation of pollen count and asthma which is typical allergic disease in South Korea. Method: All asthma cases of South Korea (2006~2010) composed of J45.0 and J45.9 from ICD-10 code were counted in the Reports of National Health Insurance Corporation. Meteorological data (average temperature and precipitation), and three area (Seongdong-gu, Guri, & Jeju) pollen counts (weekly added value of Birch, Alder, Oak, Ragweed, Wormwood, Japanese hop, Grass, Hazel) were provided by National Institute of Meteorological Research, and air pollution data (CO, NO2, O3, PM10, SO2) by National Institute of Environmental Research. We used General Additive Model to see relative risk of occurrence of asthma, when weekly pollen count is more than 10 compared to less than 10. Other meteorological and air pollution data were adjusted. Results: Number of asthma case is increasing every year from 2006 (6,939,178) to 2010 (15,633,105). Total count of asthma for five years is 65,602,525. Occurence of asthma was increased with pollen counts of Oak, Birch in Seongdong-gu, Grass, Hazel, Oak in Guri, and Alder, Oak, Hazel, Birch. But some pollen count increase was shown to reduce occurrence of asthma. Conclusion: Occurrence of asthma in South Korea is increasing every year and may be associated with some pollen counts. Some pollen decreased asthma occurrence. Maybe pollen in addition to a variety of causes affect occurencece of asthma. Difference of the pollen effects by area would be due to the latitude of the region.