Memristor-based gas sensor (Gasistor) has physical limitations because the target gas is detected through the top electrode (TE). In this paper, we used CNTs with a porous structure as the TE to address this limitation. Furthermore, by decorating CNTs-TE with N-[3-(Trimethoxysilyl)propyl] ethylenediamine (en-APTAS), the functional groups interacted with the target gas to increase the probability of adsorption and improve the response. As a result, the proposed gasistor with CNTs-TE decorated with 1.5 wt% of en-APTAS exhibits a high response of 47 at 50 ppm, which is five times higher than that of a gasistor with a conventional metal TE.