In construction work on soft soil, the design and evaluation of the soil improvement effect are important. This paper describes the strength deformation characteristics of cement stabilized soils with a wide range of water to cement weight ratios (W/C ratio) and soil to cement weight ratios (S/C ratio). The effects of mix proportion conditions and curing time on stress-strain behavior of cement stabilized soils are shown quantitativcly. The unconfined compressive strength of cement stabilized soils can be represented as a hyperbolic relationship between unconfined compressive strength and curing time. Increasing S/C ratio and decreasing W/C ratio lead to increases instrength and stiffness. Several empirical relationships between unconfined compressive streength and curing time have been also developed.