Forming of tufted preforms enables a rapid production of double-curved through-thickness reinforced composites. However, the presence of tufting yarns constrains the interlayered slippage and alters the deformation mechanism of the preforms, which becomes an obstacle restricting the wider application of tufted composite parts. In this study, the variable frictional force caused by tufting yarns is modelled using connector elements. The differences in simulation results between variable friction, constant friction and rigid friction are revealed. The proposed model can predict multiple forming behaviors (such as in-plane shear angle, tufting yarn slippage, interlayer sliding, wrinkling defect, etc.) across a wide range of tufting parameters. This method can be applied to structural designs and parameter optimization for tufted composites.