The invention relates to a 
powder feeding 
system of a nano 
powder preparation process. The 
powder feeding 
system comprises a storage bin, a spiral feeder, a powder feeder and a flexible 
pinch valve. The storage bin is provided with a material level meter, and a feeding screw rod in the spiral feeder is connected with a speed regulating motor through magnetic 
coupling. The 
diameter of the powder feeder is larger than the inner 
diameter of a powder feeding 
barrel, and a plurality of feeding through holes are arranged in the circumferential direction of a powder feeding disk. When the powder feeding disc rotates, the feeding through holes which are screwed out of the inner cavity of the powder feeding 
barrel correspondingly communicate with a discharging hole and an air inlet hole. The flexible 
pinch valve comprises a rubber tube and two pairs of pinch rods, and each pair of pinch rods are connected with an electric push rod. When the electric push rod moves, the pair of pinch rods clampthe rubber tube. An air tap is arranged at the 
discharge end of the rubber tube; the air tap is connected with a vacuumizing device and a working gas recharging device. The powder feeding 
system of the nano powder preparation process solves the problems of sealing, transmission, conveying and the like of micron-level powder raw materials which are difficult to solve in the powder feeding process,and the delivery value of the powder raw materials can be stably and accurately controlled, so that the 
plasma flame flow is stable, and the required particle size of nano powder is further achieved.