Abstract: In order to understand the (hydroxyamino)acetic acid （HAAA） of reduction performance to Pu(Ⅳ), the kinetics of reaction between Pu(Ⅳ) and HAAA in nitrous acid solution was determined by spectrophotometrically method. The rate equation is －dc(Pu(Ⅳ))/dt＝kc(Pu(Ⅳ))c^1.50(HAAA)c^-1.00(H+) c-^0.63(NO^－₃), where reaction rate constant k=(42.1±4.2) (mol/L)^－0.13•s^－1 at 15.8 ℃. The activation energy Ea is (78.0±1.6) kJ/mol. Effects of c(HAAA), c(H+), c(Fe³⁺), c(UO²⁺₂), ionic strength and temperature on reduction rate of Pu(Ⅳ) were investigated. Pu(Ⅳ) can be reduced to Pu(Ⅲ) rapidly by HAAA under usual conditions. The reaction rate can be accelerated by increasing concentration of HAAA, decreasing HNO₃ concentration and ionic strength as well as rising temperature. The influence of UO²₊2 on reaction rate is negligible. The application of HAAA in the separation between Pu and U is promising.