The invention relates to a design method of a supersonic laval nozzle structural alloy melt atomizer, and belongs to the field of alloy powder atomizing preparation. According to the design method, asupersonic laval wall curve is researched, the characteristic of close coupled atomization is combined, the supersonic laval nozzle structural atomizer is designed according to the suction pressure criterion, the close coupled criterion and the flow velocity criterion, and the influence of five main factors including the atomization gas pressure, the atomization gas temperature, the gas nozzle hole heart distance, the gas injection angle and the extended length of a diversion pipe on the flow field structure is simulated and researched by utilizing computational fluid dynamics software. Thus,structural parameters of a nozzle can be optimized, the phenomena of gas backflow and back spray are avoided, the atomizing efficiency is improved, and a guarantee is provided for the production of alloy powder. According to the atomizer, the phenomena of blockage of the diversion pipe, gas back spray and the like of the atomizer can be prevented, shock wave and turbulent flow are reduced, the flying distance of gas can be reduced, the flow velocity can be increased, and the loss of energy is reduced.