Based on the results of pull-out test on geotextiles, this paper presented a three-staged model for total shear stress-displacement to consider the strain softening and plastic flow. According to the mechanical characteristics of geotextiles, the non-linear differential equations are expressed in non-dimensional form and solved numerically using a finite difference method. The variation of the displacement, strain, tension and shear stress in pull-out test can be obtained. The relation between pull-out force and deformation was discussed based on the example analysis, and compared with the experimental pull-out test results. Comparison with the results of linear elastic model and hyperbolic model shows that three-staged elastic-plastic model is in good accord with practical situation.