The load transfer efficiency from surrounding matrix to the carbon nanotubes (CNTs) in the CNTs nanocomposites was studies. Both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) were taken into account in the investigation. A cylindrical representative volume element (RVE) containing the CNTs and polymer phases were employed in the shear lag analysis from which the axial stress distribution as well as the load transfer efficiency in the CNTs was characterized. The van der Waals interaction of the adjacent graphite layers in the MWCNTs was described using an interfacial region with low shear stiffness. For the sake of comparison, a covalent bonding between the graphic layers was assumed and modeled using an interfacial region with high shear stiffness. Results indicated that the SWCNTs exhibit superior load transfer efficiency than MWCNTs associated with the same CNT volume fraction in the composites. This is attributed to the fact that in the MWCNTs, the load carrying capabilities reduce as the number of graphic layers increase. Moreover, it is revealed that the deficient load transfer efficiency in the MWCNTs may not be improved even though the covalent bond between the graphite layers is constructed.