Abstract: MULTINUCLIDE METHOD FOR DETERMINATION OF FISSION QUANTITY OF MIXED FISSILE MATERIALDING YUZHEN ;YANG YUSHENG ;CHANG YONGFU WANG JUN ;LU JIACHUN;LIU DEMIN（Northwest Institute of Nuclear Technology，Xi’an，710024）ABSTRACT A new methd──multinuclide method is proposed for the determination of fission quanti-ties of mixed fissile material．Both total fission quantity and partial fission quantities of individualfissile materials can be obtained simultaneously by determining the number of nucleus of some fis-sion products with linear least-square method，in which the virtual fission quantity is y axis andthe ratio of fission yields for fissile materials is x axis，i．e.n_i is virtual fission quantity；y~A_i is yield of fission product i for fissile material A；Y~B_i is yield of fis－sion product i for fissile material B；n~A_f is fission quantity of A；n~B_f is fission quantity of B；A and Bare fissile materials，The intercept at yaxis is fission quantity of A and the n_i vaule at Y~B_i／Y~A_i＝1 istotal fission quantity．The key of using this method is how to select fission products and theiryields，The rule of selection of fission preducts is discussed.Key words Multinuclide method Fission quantity Fission－preducts Yield Mixed fissile material