The electronic transport properties of the thin film transistor (TFT) devices consisting of carboxyl-modified single-walled carbon nanotube (c-SWCNT) network are studied. This work is focused on the analysis of the effect of chemical treatment on the electronic transport properties from these devices. The c-SWCNT thin film transistor (c-SWCNT TFT) devices were fabricated by a directed assembly method based on electrostatic interaction between amino-functionalized substrate and c-SWCNTs. The electrical characteristics of c-SWCNT TFTs were measured at room temperature. From the Raman results and the transport characteristics of c-SWCNT TFT devices, the transport mechanism in these devices can be accounted that the deep levels arising from vacancy-adatom complex induced the changes in the electronic band structure of SWCNTs.