Strength characteristics play an important role in mechanic behavior of cement-soil. Laboratory tests on cement-soil with 12% cement ratio and 28 d curing time are conducted by using a new multifunctional triaxial apparatus under fixed spherical pressure condition. Seven series spherical pressures are designed to apply, namely 300 kPa, 400 kPa, 500kPa, 600 kPa, 800 kPa, 1000 kPa, and 1200 kPa. At the same time, seven series consolidation pressures are taken into accounted. Tested data show that: (1) the stress-strain curve of cement-soil is characterized by strain softening, and the soften rate is related to confining pressure; (2) shrinkage or dilatancy of cement-soil volume strongly depend on the value of loaded spherical pressure; (3) failure curve of cement-soil is approximately a line and it agrees with the Mohr-Coulumb criterion. The result of this paper is helpful to the numerical analysis and practical engineering design of cement-soil foundation structures.