A new type of gas sensing material based on metal oxide modification multi wall carbon nanotube (MO/MWCNT) composites is presented since the interface between the composites enhance the carrier density so as to improve the gas sensitivity. Three kinds of MO/MWCNT composite materials, such as ZnO/MWCNT, SnO2/MWCNT and TiO2/MWCNT, have been acquired in situ growth using catalytic pyrolysis method. The MO nano particles have decorated on side of MWCNTs, whereas the introduction of SnO2 nano particles makes part of MWCNT showing two-dimensional form of carbon nano-wall structure. Among four kinds of cathode of ZnO/MWCNTs, SnO2/MWCNTs, TiO2/MWCNTs and pure MWCNT composite film, TiO2/MWCNTs composite has the lowest threshold electric field required to draw current of 12 mu A has been found to be similar to 1.2 V/mu m, and also TiO2/MWCNTs composite has the highest sensitivity of 16% to ethanol. The TiO2/MWCNTs composite is superior to the others both in vacuum electron transportation and gas sensitivity. (C) 2011 Elsevier B. V. All rights reserved.