In this paper, a green process for the synthesis of N,N,N-trimethyladamantan-1-aminium hydroxide was reported. Firstly, the precursor N,N,N-trimethyladamantan-1-aminium salt was obtained by using 1-adamantanamine as raw material, dimethyl carbonate (DMC) as methylating reagent. Then, the precursor was reacted with calcium hydroxide to achieve the final product N,N,N-trimethyladamantan-1-aminium hydroxide. The structures of ammonium salt and hydroxide were characterized by 1H NMR and 13C NMR spectra. After investigating the effects of catalyst, mole ratio of reactants, reaction temperature and time on the yield of N,N,N-trimethyladamantan-1-aminium salt, the optimum reaction conditions were obtained as follows: N,N-dimethyl formamide (DMF) was used as the catalyst, m(DMF):m(1-adamantanamine) = 0.25, n(1-adamantanamine):n(DMC) = 1:8, reaction temperature and time were 140 ℃ and 5 h, respectively. Under these conditions, the yield of N,N,N-trimethyladamantan-1-aminium salt could be up to 97.3%. Compared with the traditional process using dimethyl sulfate (DMS) as the methylation reagent, this process is more safe, green and efficient.