By　using　the　test　data,　the　uncertainty　of　the　dynamic　modular　ratio　G/Gmax　and　damping　ratio　λ　versus　dynamic　shear　strain　γ　for　the　conventional　soils　in　China　is　studied.　The　characteristics　of　the　uncertainty　distribution,　the　probability　indexes　as　well　as　the　range　of　G/Gmax　and　λ　for　the　typical　strains　under　different　probabilities　are　presented.　Based　on　588　groups　of　test　results　from　42　cities　and　districts　in　17　provinces　in　China,　the　uncertainty　of　the　modular　ratio　and　damping　ratio　versus　8　typical　shear　strains　is　analyzed.　The　results　indicate　that　most　of　the　uncertainty　distribution　of　G/Gmax　and　λ　is　abnormal　and　that　the　statistic　indexes　for　the　probability　are　regular.　The　standard　deviation　and　the　variation　coefficient　of　G/Gmax　and　λ　are　both　significant,　and　meanwhile　the　maximum　of　the　standard　deviation　just　appears　in　the　sensitive　range　for　the　seismic　analysis　of　soil　layers.　The　95%　reference　values　of　G/Gmax　and　λ　are　quite　different　from　the　envelopes　of　G/Gmax　and　λ　for　all　types　of　soils.　The　variation　coefficients　of　G/Gmax　increase　with　the　increase　of　the　shear　strain,　but　the　variation　coefficients　of　λ　decrease　with　the　increase　of　the　shear　strain.　The　uncertainty　of　G/Gmax　is　obvious　at　the　large　strain,　while　that　of　λ　is　obvious　at　the　small　strain.　The　variation　coefficients　of　λ　are　larger　than　those　of　G/Gmax,　indicating　the　uncertainty　of　the　dynamic　damping　is　more　remarkable　than　the　dynamic　modulus.