The detection of dissociated SF6 species, generated by partial discharge (PD), is of great importance because the dissociated compositions can alter inherent potential of SF6 and pose safety risks to power systems. Here we report that the sensitivity of carbon nanotubes (CNTs) about dissociated species of SF6 substantially increases by functionalizing with Tin oxide (SnO2). SnO2/MWCNTs nanocomposites was prepared by a simple route that included in situ growth of SnO2 on the surface of MWCNTs through hydrothermal method in this work and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis techniques. The chemical sensors based on SnO2/MWCNTs nanocomposites exhibited good sensitivity in response to decomposition components at room temperature. The work provides an appropriate functionalization methodology to conduct the dissociated SF6 species monitoring.