Research conclusions: From the prediction analysis with curve fitting method it is concluded after excavation or filling of the subgrade，the subgrade settlement is large when the subgrade stands within 4 months，the subgrade settlement tends to slow down when the subgrade stands for 4-6 months and the subgrade settlement tends to stable when the subgrade stands for more than 6 months．Although there is the difference of settlement prediction between using logarithmic curve method and hyperbola method，but the difference Call be solved by using the medium value of these two methods to ensure the prediction conforming to the real situation．