In this paper, through the experimental study on polyacrylonitrile fiber on mechanical properties of cement stabilized soil and the cement soil without side limit compression strength, splitting tensile strength, flexural strength, shear strength test and analysis were conducted. Results show that, fiber can obviously improve the cement soil of the mechanical properties of the matter. Fiber on cement soil splitting tensile and flexural strength increase is better than fiber on the compressive strength of cement soil improve. Fiber can greatly enhance the cohesion of cement soil, and under the same floating load shear strength.