The preparation, stability and decomposition of methylhydrazine oxalate (MHOX) were investigated. White needles of MHOX were prepared. The molecular formula of MHOX is (CH 3 N 2 H 4 ) 2 C 2 O 4 . The aqueous solution of MHOX is stable at ambient temperature.The kinetics of redox reaction between oxalic acid and H 2 O 2 used as an oxidant was studied. The kinetic rate equation is as followsThe kinetics of redox reaction between methylhydrazine and H 2 O 2 was also studied. The rate of decomposition of methylhydrazine is higher than that of oxalic acid. The decomposition reaction is given as follows:The proposed kinetic rate equation is as follows:The rate of decomposition of MHOX with H 2 O 2 depends mainly on that of oxalic acid.Experiments show that the washing efficiency of uranium from 30%TBP-kerosene (OK) used with MHOX is the same as that with Na 2 CO 3 . The washing efficiency of Pu and Am with MHOX is greater than that with Na 2 CO 3 .