The objective of this research is to discuss the regional development which was affected by the earthquake disaster, and to take the population sector of Nan-To County as the empirical topic, to utilize catastrophe model to describe and explain the present residential population affected by the catastrophe. According to the result of the catastrophe cusp model, it shows that the unemployment rate and the government expenditure on each person are the two principal factors to the population fluctuation. The fluctuation of population occurs when the unemployment rate increases rapidly due to earthquake.