Abstract: The paper deals with the dependence of the colloid formation of niobium on the concentration of nitric acid and self niobium. The different concentration of niobium in the range of 1×10~(-6) to 8×10~(-5)mol/l and nitric acid in the range of 0.5 to 8.0 mol/l was investigated for observation of colloid formation by ultracentrifugation. The results show that the colloid niobium is not formed when niobium concentration is lower than 1×10~(-6) mol/l. If niobium concentration is higher than 7×10~(-6)mol/l, the colloid is observed obviously and colloid formation of niobium is increasing quickly when concentration of niobium is higher than 1×10~(-5)mol/l. The particles of colloid seem to be polydispersed when nitric acid concentration is lower than 3mol/l and monodispersed when nitric acid concentration is higher than 3 mol/l.