The soil-cement is applied in hydraulic engineering, construction engineering and highway engineering. It needs take much time and energy to do the experiment of soil-cement design, because the influence factors of soil-cement unconfined compressive strength are many. The study is based on the former experimentations, and quantitative analyzed relationships among soil-cement unconfined compressive strength, earthiness, cement mixing amount and curing time by nonlinear curve fitting. Then, rational experience formula is given in this paper. It is tested in Nantong Building foundation excavation project, and the result proves that formula is practical.