Soil　liquefaction　is　a　major　cause　of　site　damage　during　earthquakes.　Since　Casagrande＇s　works,　significant　progress　has　occurred.　But,　most　of　these　are　applicable　for　sandy　soils＇　So,　based　on　the　former　research　and　the　dynamic　triaxial　test,　some　questions　are　analyzed,　including　the　mechanism　of　silty　soil　liquefaction　and　some　factors,　such　as　the　clay　particle　content,　the　relative　density　and　the　structure　of　the　soil,　which　impact　on　the　liquefaction　strength　of　the　silty　soils.　The　pore　water　pressure　is　also　studied.　Considering　that　the　number　of　cyclic　loading　is　non-continuous,　a　new　applied　model　is　proposed　to　evaluate　the　pore　water　pressure,　which　is　expediently　applied　into　the　finite　element　method　programs.