Abstract: To obtain an accurate solution for the undrained cylindrical cavity expansion in over-consolidated clay considering the influence of K₀, this study uses the Clay and Sand Model (CASM) yield criterion, adopts the classic stress-dilatancy relationship, and fully considers the static soil pressure parameter K₀ and the heavy over-consolidation ratio. The non-associated flow rule is used to transform the stress space, and then the solution model of first-order partial differential equations is established for the undrained cylindrical cavity expansion in the over-consolidated clay under the influence of K₀. According to the known stress and displacement conditions of the elastoplastic boundary, the accurate solution of the cylindrical cavity expansion model is determined by a numerical solution method. Comparing the modified Cambridge model (MCC) solution, the Modified Cambridge model (SMP-MCC) solution based on SMP yields criterion and the solution of unified hardening model of clay and sand (CSUH), the parameter analysis show that: when the soil OCR ≤2, the method proposed can simulate the yield stress and failure stress of the soil element well. When the soil OCR>2, this method overcomes the overestimation of yield stress and failure stress of over-consolidated clay. When K₀ changes from 1.0 to 2.5, the normalized ultimate expansion pressure changes from 5.4 to 3.2; the normalized ultimate expansion excess pore water pressure changes from 2.4 to 1.0. And the practicality and correctness of this method are verified by field measured data.