Objective   To study the changes of intervertebral contact area during lumbar spondylolisthesis and discuss its clinical effects.   Methods   The images of superior surface of L5 vertebras and inferior surface of L4 vertebras from 25 cases were taken by a digital camera, and then spondylolisthesis procedure in 2D plane was simulated by computer with the step of  fourteen, while intervertebral contact area (Sn) of every step was measured by Image-Pro Plus software. Results  During lumbar spondylolisthesis procedure,  Sn% （Sn%=Sn/S*100%）showed a hyperbola changes. Sn% lost slowly during the rate of 0~23%, then lost quickly during 23%~44%, finally slowly once again after the rate of 44%. The inflection points appeared at the rates of (23±2.02)％ and (44±1.46)％.  Conclusions   The intervertebral contact area presents a non-linear change, which is helpful to judge the stability of lumbar spine and guide stable reduction during spondylolisthesis operation.