The surface adsorption is considered to be a very important factor in photodegradation process, especially in the removal of gaseous pollutants. In this work, nitrogen doped reduced graphene (N-GR)/TiO2 were synthesized to probe the polarity adsorption and photodegradation characteristics of acetaldehyde (polar) and ethylene (nonpolar). Morphology and properties of the samples were revealed by TEM, Raman spectra, photoluminescence spectra, photocurrent, electron spin resonance and so forth. Adsorption of flowing gas and TPD were used to indicate the adsorption ability of the composites towards acetaldehyde and ethylene. In experiments, the difference of nitrogen doping amount can adjust the polarity of N-GR/TiO2 composites efficiently and then influence their photodegradation performance. Specifically, the N-GR/TiO2 showed higher acetaldehyde adsorption capacity than GR/TiO2, while the GR/TiO2 possessed the highest adsorptive abilities in ethylene case. In the subsequent photodegradation tests of flowing acetaldehyde, all of the N-GR/TiO2 samples had removal efficiencies higher than that of GR/TiO2. The highest removal efficiency reached by the 2 N-GR/TiO2 is around 82%. In the ethylene to contrast, the removal efficiency was obtained as 93.8% by GR/TiO2, which is higher than that of the N-doped samples. It can be seen that the high polarity samples could improve the adsorption and photodegradation performance of polar molecules, which could propel the understanding and application of photodegradation technologies.