sIn this paper, a series of graphene (G)-NiGa2O4 nanocomposites were prepared by hydrothermal method. The as-prepared nanocomposites were characterized by XRD, SEM, HRTEM, FTIR, Raman, XPS and nitrogen adsorption-desorption, respectively. The effect of the amount of graphene in the nanocomposites on the gas sensing responses and gas sensing selectivity of G-NiGa2O4 nanocomposites was investigated. It was found that the addition of graphene in nanocomposites increased the responses of nanocomposites to trimethylamine (TMA) when operating at 20 °C and 2 wt% G-NiGa2O4 nanocomposite showed the best gas sensing performances among all studied nanocomposites. 2 wt% G-NiGa2O4 nanocomposite exhibited high gas sensing selectivity to TMA at room temperature, the ratio of S 1000 ppm TMA/S 1000 ppm ammonia reached 36.1; the detection limit for TMA reached 0.01 …