Abstract: Simulation of static penetration of cone in the undrained clay and analyses of its influence factor are taken as the research objectives. It is assumed that the soil is idealized as a homogeneous elastic and perfectly plastic material obeying the Von-Mises yield criterion. An Arbitrary Langrangian-Eulerian (ALE) technique is adopted to preserve the quality of mesh under the condition of large-strain for performing large strain finite element numerical simulation. The influences of the rigidity index, in situ stress state and the cone roughness on the radius of the plastic zone and the cone factor under steady-state conditions are analyzed and a theoretical correlation for the cone factor is developed in this study. The simulation results show that the plastic zone increases with the increasing rigidity index, the radial expansion of the plastic zone around the cone tip is between the cylindrical cavity expansion and the spherical cavity expansion, which is closer to the spherical cavity expansion. The cone factor increases with the increasing rigidity index and the cone roughness while the cone factor decreases with the increase of in situ stress state parameter. The formula for the cone factor proposed in this article can be used to quantify the effects of the soil rigidity index, in situ stress state and the cone roughness with reasonable accuracy. The research results are helpful to understand the mechanism of CPT and improve the calculation accuracy of the undrained shear strength.