Winter phenology (diapause and activity) of insects is expected to change more greatly compared with those of other seasons, because the temperature in winter increased higher than those in other seasons in the temperate regions. However, studies on changes of insect winter phenology due to climate warming are rare. It is expected that winter flights of flies (Diptera) will increase as climate warms. This study is aimed to predict the increase of fly winter flight according to temperature increase using the relationship between the flight and temperature. The survey on flies and weather (temperature and rainfall) was carried out in the Hongneung arboretum in Seoul. Flies were collected weekly from December 2012 to February 2013 using sweeping and Malaise trap. In the survey, 106 flies belonging to 28 morpho-species and 17 families were collected. Richness and abundance of flies were positively correlated with temperature. The increase of fly winter flight (richness and abundance) was projected according to temperature rise using the regression models for relationships between the fly flights and temperature.