Abstract: Because the crude niobium ore is difficult to be used,according to the composition analysis and phase analysis of crude niobium ore,the KOH hydrothermal method was used to research the dissolution of crude niobium ore and the dissolution of crude niobium under hydrothermal system was researched by changing the temperature and the KOH concentration.The results show that the dissolution of niobium from crude niobium ore could reach 90%,at 30% of KOH concentration,and 200℃;the dissolution of niobium increased first and then decreased with the increasings of KOH concentration and temperature;in the whole process of the dissolution,the alkaline components Fe,Mn,Mg kept a low dissolution yields.XRD and SEM’s results show that the increasings of KOH concentration and temperature accelerated the decomposition of (Fe,Mn)(Nb,Ta)₂O₆.When the KOH concentration was 30%,and the temperature was 200℃,continuing to strengthen the reaction conditions,the dissolution of Nb decreased significantly owing to the transformation from soluble K₈Nb₆O₁₉ to insoluble KNbO₃.