Abstract: The present invention relates to an asymmetric synthesis method of a chiral intermediate (S,S)-2,8-diazabicyclo[4,3,0]nonane (I) of moxifloxacin, wherein an imide or enamine compound is obtained by dehydration reaction of the pyrrolidine-3-ketone as shown in formula (II) and chiral amine(R)-1-phenylethylamine, followed by the reduction of the imide or enamine compound to obtain a compound of formula (III) or (IV) having the chiral structure of formula (I), and then a compound of formula (I) is obtained by intramolecular cyclization, and removal of the chiral auxiliary group and amino-protecting group. The present invention also relates to pyrrolidine-3-ketone as shown in formula (II) and a preparation method therefor, and in the formula (I), (II), (III), (IV), R is an amino-protecting group, especially C1-4 alkoxycarbonyl, benzyloxycarbonyl or benzyl which can be removed by hydrolysis or hydrogenation.