SnO2:CNT thick films for gas sensors were fabricated by screen printing method on alumina substrates and were annealed at 300 oC in air. The nano SnO2 powders were prepared by solution reduction method using tin chloride (SnCl2.2H2O), hydrazine (N2H4) and NaOH. Nano SnO2:CNT sensing materials were prepared by ball-milling for 24h. The weight range of CNT addition on the SnO2 surface was from 0 to 10 %. The structural and morphological properties of these sensing material were investigated using X-ray diffraction and scanning electron microscopy and transmission electron microscope. The structural properties of the SnO2:CNT sensing materials showed a tetragonal phase with (110), (101), and (211) dominant orientations. No XRD peaks corresponding to CNT were observed in the SnO2:CNT powders. The particle size of the SnO2:CNT sensing materials was about 5~10 nm. The sensing characteristics of the SnO2:CNT thick films for 5 ppm H2S gas were investigated by comparing the electrical resistance in air with that in the target gases of each sensor in a test box. The results showed that the maximum sensitivity of the SnO2:CNT gas sensors at room temperature was observed when the CNT concentration was 8wt%.