Aimed　at　the　problem　of　sand　soil　roadbed　of　a　freeway　impregnated　in　water,　soil　was　cored　for　the　statistical　result　of　nonlinear　parameters　by　3-axial　experiment.　The　parameters　of　soil　properties,　such　as　K　and　Kb　which　had　more　variability　than　the　others　were　simulated　as　stationary　Gaussian　processes.　The　local　average　theory　of　2-D　random　field　was　applied　for　the　processes.　The　Duncan-Chang　nonlinear　constitutive　law　was　also　applied　for　the　second　order　nonlinear　perturbation　stochastic　finite　element　method　and　the　algorithm　was　also　put　forward.　The　reliability　of　wetting　deformation　and　stability　of　the　sand　soil　roadbed　was　analyzed.　As　a　result,　the　roadbed　will　evolve　additional　deformation　when　the　sand　soil　is　impregnated,　while　the　variability　of　soil　mechanical　parameters　shows　less　influence　on　the　deformation　of　roadbed　and　pavement.　Even　though　the　mechanical　parameters　of　soil　will　decrease　when　it　is　impregnated,　the　reliability　index　of　the　roadbed　stability　is　still　so　high　that　there　is　less　possibility　that　the　roadbed　will　slide　failingly.