The utility model relates to a device for preparing powdery alpha-olefin sulfonate. The technical problem to be solved is that the provided device is necessary to have the features of being low in energy consumption, compact in apparatus structure, less in investment, less in byproduct sultone, easy to control system and stable in operation. The technical scheme is as follows: the device for preparing powdery AOS comprises a feeding device, a spray drying tower, a cyclone separation device and a dust-collection device which are communicated in order through a pipeline, and is characterized in that the top end of the spray drying tower is provided with a feeding port and a dry air inlet communicated with the feeding device, the side of the spray drying tower is provided with a mixed airflow outlet communicated with the cyclone separator, and the bottom of the spray drying tower is provided with a cleaning outlet of a sludge treatment system.