A study on methylamine (MA) photo-dissociation in gas phase has been carried out using UV radiation from a 207 nm KrBr* excilamp driven by a sinusoidal electronic control gear. The influence factors including gas flow rate, initial concentration and input power of removal efficiency were investigated. The radiant power and spectrum of the lamp were measured. Several parameters were investigated including removal efficiency, energy yield, carbon balance and CO2 selectivity in order to comprehensively evaluate the photo-dissociation process. It was shown that the removal efficiency increased with enhanced input power, decreased gas flow rate and increased MA initial concentration. Energy yield had positive pertinence with MA initial concentration, and it would obtain optimal value at 65.1 W. Carbon balance and CO2 selectivity showed slighter enhancement when lamp power increased and gas flow rate declined. The removal efficiency of 56.8% was achieved at a lamp power of 79.8 W, a gas flow rate of 9.0 m3 x h(-1) and an MA initial concentration of 2 897 mg x m(-3). Under the above mentioned experimental conditions, energy yield reached 185.6 g (kW x h)(-1), and carbon balance and CO2 selectivity were 16.8% and 10.3%, respectively. At last, secondary products formed were analyzed by gas chromatography-mass spectrometry and the photo-degradation mechanism of MA was suggested on the basis of UV-vis absorption spectrum.