Abstract: A quasi-static finite element approach is presented to simulate soft tissue deformation during robot-assisted needle insertion with satisfactory precision. Based on the needle force analysis and soft tissue deformation attributes,the dynamic process of soft tissue deformation during needle insertion is decomposed into a set of discrete quasi-static stages. At each stage,we derive the two and three dimensional quasi-static finite element models by ANSYS software with superposed element method. Experimental results demonstrate the validity and the applicability of our method for soft tissue deformation.