Pt or Pd decorated CNTs have received considerable attention in recent years as gas adsorbent and sensors due to their strong catalytic property towards gas interaction. In this work, we theoretical simulated the adsorption process of SF6 decomposed species, namely SOF2 and SO2F2 onto Pt and Pd co-decorated CNT (PtPd-CNT) based on density functional theory (DFT) method, in order to propose novel kind of sensing material applied in the field of electrical engineering. To further elucidate the co-decoration effect of Pt and Pd atoms on the adsorption performance of CNT upon two gases, a cluster of Pt2Pd2 is applied to decorate the CNT surface with gas adsorption process simulated as well. Results indicated that such material has better sensitivity upon SOF2 than SO2F2, given the stronger adsorption behavior and larger change in conductivity after adsorption, showing its potential to be exploited as gas sensors for detection of the former gaseous substance. Our calculation would be meaningful to suggest novel material realizing the operation state evaluation of SF6 devices.