The NOx emission under acoustic excitation and no-excitation were compared on methane laminar partially premixed flame. The mechanism of NOx was analyzed by micro-thermocouple, water-cooled sampling probe. The experimental results show that compared with no-excitation combustion, pulsating combustion produced less NOx emissions. There are two reasons including: (1)peak temperature was reduced and the distribution of temperature was more uniform, (2)the oxygen of flame was increased for rapid mixing rate and the reaction rate was enhanced.