The invention discloses a system and method for producing high-purity vanadium pentoxide powder, belonging to the fields of chemical engineering and materials. According to the invention, fluidizing low-temperature chlorination is used for converting industrial-grade vanadium pentoxide into vanadium oxytrichloride; through heat exchange between fluidization gas and chlorination flue gas, chlorination gas is preheated; a proper amount of air is added to allow a part of coke powder to combust, thus providing a balanced supply of heat during the process of chlorination, improving chlorination efficiency, and ensuring good selectivity of low-temperature chlorination; and the vanadium oxytrichloride is subjected to fluidized-vapor-phase hydrolysis and fluidized calcination after distillation and purification to produce a high-purity vanadium pentoxide product and a by-product, i.e., a hydrochloric acid solution. The system and method have the advantages that raw materials are good in adaptability, no polluting wastewater is discharged, low energy consumption in production and low cost in operation are realized, product quality is stable, etc.; and the system and method are applicable to large-scale industrial production of high-purity vanadium pentoxide having a purity of 4N or higher and have good economic benefits and social benefits.