The invention relates to a laser energy modulation welding method and belongs to the technical field of laser material processing. The laser energy modulation welding method is characterized in that during welding, power modulation output welding is performed through laser energy according to certain modulation frequency and the laser welding characteristic time (the spot diameter is divided by welding speed). The specific characteristics include that the laser output constant power time t1 and the laser output modulation power time t2 occur alternately, and the alternate frequency is 10 Hz-500 Hz; and within the t2 time period, the laser power ranges from zero W to P (P is the constant power within the t1). Selection of the t1 and the t2 is related to the welding characteristic time. Thewelding method has the advantages that laser energy input can be reduced substantially, the acute evaporation process of a molten bath is weakened, deformation of a welded part is reduced obviously, and the welding penetration is nearly not affected; and the manufacturing energy consumption is reduced substantially, and thus the welding manufacturing process is more environment-friendly.