Liquidity　index　is　used　to　measure　the　relative　consistency　of　natural　soils,　making　it　possible　to　evaluate　the　stiffness　degree　and　strength　of　clays.　However,　a　systematic　understanding　of　the　relationship　between　the　undrained　shear　strength　and　the　liquidity　index　remains　unclear.　While　some　studies　are　being　conducted　on　this　putative　relationship,　the　theoretical　foundation　is　still　lacking.　This　study　proposes　a　new　undrained　shear　strength　prediction　model　based　on　the　Mohr-Coulomb　failure　criterion　and　the　critical　state　theory.　A　database　of　103　soil　samples　from　18　research　is　utilised　to　validate　the　model＇s　applicability.　The　results　reflect　a　consistent　level　of　accuracy.　The　proposed　model　has　an　obvious　advantage　and　has　potential　for　predicting　the　undrained　shear　strength　of　clays.