Abstract: The extraction properties and mechanism of niobium thiocyanate complex with secondary amine 7203 are studied. The extraction dependency of niobium on the properties of diluent, the amounts of additive and the stripping condition is also discussed. The compositions of the extractive species, (ANH2) NbO(CNS)4 or (ANH2) Nb (OH)2 (CNS)4, are determined by the slope method , saturation method , etc. The extraction reaction can be expressed as follows:The possible extraction mechanism is proposed