Abstract: Annual mean air temperature, monthly mean air temperature and the extreme air temperature in Yingkou from 1951 to 2005 were analyzed. The results show that annual mean air temperature has an increasing tendency during the recent 55 years. The minimum air temperature increases greatly, followed by mean air temperature and the maximum air temperature. The extreme maximum air temperature decreases from 1950s to 1980s and then increases from 1980s to 2000s, especially from 1980s to 2000s, which is different from the annual mean air temperature. The difference of the extreme maximum air temperature change rate among different months is not significant. The extreme minimum air temperature increases during recent 55 years, especially recent 30 years, while it is stable during recent 20 years. The monthly extreme minimum air temperature is an increasing tendency, which is obvious in winter and becomes weak in summer. Heat island effect caused by urbanization and industrialization is the main reason for the temperature increasing, and the global warming makes it stronger.