The present study investigates the interfacial properties of carbon nanotube (CNT)-reinforced polymer composites by simulating nanotube pull-out. A finite element model of the noncovalent van der Waals interaction between CNTs and polymer via pull-out method has been developed to evaluation of the interfacial properties of CNT–polymer interphase. The Lennard-Jones interatomic potential was employed to simulate a nonbonded interphase. In this method, the interfacial shear stress during displacement of CNT has been determined directly through calculating shear force on surface of each carbon atom during pull-out. The shear stress distribution along CNT length for better understanding of pull-out results has been determined as novelty of this method. This model successfully obtains the maximum pull-out force to calculate interfacial shear strength (ISS). The research findings contribute to a better understanding of the load transfer on the tube–polymer interphase through CNT and the tube’s reinforcing mechanism. Based on the pull-out modeling technique, the effects of CNT length on pull-out force, ISS and stress have also been analyzed in details. The results indicated that, with the increase in the embedded 74length of nanotube, the interface debonding process leads to an unchanged debonding force when the embedded length exceeds a threshold value named as “critical embedded length”; also, the ISS has been decreased with increase in CNT length. In this method clearly difference between catastrophic and noncatastrophic CNT debonding during pull-out with change in the embedded length of CNT have been investigated.