This paper describes the exploration of a synergic effect within n-type inorganic-p-type organic nano-hybrids in gas sensors. One-dimensional (1D) n-type SnO2-p-type PPy composite nanofibers were prepared by combining the electrospinning and polymerization techniques, and taken as models to explore the synergic effect during the sensing measurement. Outstanding sensing performances, such as large responses and low detection limits (20 ppb for ammonia) were obtained. A plausible mechanism for the synergic effect was established by introducing p-n junction theory to the systems. Moreover, interfacial metal (Ag) nanoparticles were introduced into the n-type SnO2-p-type PPy nano-hybrids to further supplement and verify our theory. The generality of this mechanism was further verified using TiO2-PPy and TiO2-Au-PPy nano-hybrids. We believe that our results can construct a powerful platform to better understand the relationship between the microstructures and their gas sensing performances.