As the development of technology, there are many advanced methods to solve the problems of global warming. To orient the innovative controlling of global warming, this paper combines the fixed effect model with mathematics to study the effect of extreme high temperatures on internal migration in China using large data set. One more day exposure of high-temperature day in the past five years, on average, causes a 0.035 percentage points increase in the county's immigration rates. This effect is larger for a higher temperature level and is monotonically decreasing as the decrease of the county's urbanization level. Additionally, this paper also provides supporting evidence for rural-urban migration and regional heterogeneity. Back-of-the-envelop calculation shows a 66.03% increase in the mean of immigration percentage points caused by the increased extreme high temperatures from 1990 to 2005.