In this paper presents the study of the process of interaction between helium (He) and methane (СH4) molecules and the energy barrier created by a single-layer carbon nanotube. The interaction potential fields for the case of a tube as a nano-scale object interacting with single molecules or atoms were determined. Calculations show the dependence of molecular velocity within the symmetry axis of a single-layer carbon nanotube on the axial coordinate. The influence of the tube radius on the character of molecular passage through the open tube is considered.