How to prepare niobium oxalate

The invention relates to a preparation method of a water-soluble niobium compound, in particular to niobium oxalate, which comprises the following steps: adding a niobium precursor compound into an oxalic acid solution with a concentration of 200-1000g/L according to the molar ratio of oxalic acid to niobium11,and controlling the reaction temperature at 90-/kloc. The reaction time is 10 ~ 30 min or until the solution is completely clarified, the solution obtained after the reaction is crystallized, then filtered and dried. The invention provides a production method of a water-soluble niobium compound-niobium oxalate, which can be used as an additive for catalysts, ferrites and dielectric materials. As an additive in ferrite and dielectric materials, water-soluble niobium oxalate avoids the uneven distribution of niobium ions in the materials.