The present invention provides a system and method for producing high-purity vanadium tetraoxide powder. Industrial grade vanadium pentoxide is converted to vanadium oxytrichloride by low temperature fluidizing chlorination, wherein chlorinating gas is preheated via heat exchange between fluidizing gas and chlorination flue gas, and an appropriate amount of air is added to enable a part of carbon powder to combust so as to achieve a balanced heat supply during the chlorination, thereby increasing the efficiency of chlorination and ensuring good selectivity in low temperature chlorination. The vanadium oxytrichloride is purified by rectification, and then subjected to fluidized gas phase hydrolyzation, thereby producing a high-purity vanadium pentoxide product and a by-product solution of hydrochloric acid, and further obtaining a high-purity vanadium tetraoxide powder product through fluidized hydrogen reduction. The system and method have advantages of favorable adaptability to a raw material, no discharge of contaminated wastewater, low energy consumption and chlorine consumption in production, stable product quality and so on.