The invention relates to an asymmetric synthesis method of (S,S)-2,8-diazabicyclo[4,3,0] nonane (I) as a chiral intermediate of moxifloxacin. The asymmetric synthesis method comprises the steps of: firstly, carrying out a dewatering reaction on a 3-pyrrolidone compound (shown as formula III or IV) and chiral amine, reducing a dewatered product to obtain enantiopure compounds shown as a formula (II) under different reducing conditions, and carrying out intramolecularly cyclization and removal of chiral prothetic groups on the compounds shown as the formula (II) to obtain (S,S)-2,8-diazabicyclo[4, 3, 0] nonane (I). The invention also relates to 3-pyrrolidone shown as a formula (III) or (IV) and a preparation method thereof, wherein R is an amino protection group; in the formula (II), * is a chiral center mark of the chiral prothetic groups, R1 and R2 are respectively C1-4 alkyl, C1-4 hydroxyl or carboxyl substituted C1-4 alkyl, aryl, carboxyl, C1-4 carbalkoxy or carbamoyl, when Z is H2, Y is chlorine, bromine, iodine or hydroxyl sulphonate, when Z is O, Y is hydrogen, hydroxyl or C1-4 alkoxy; in the formula (III), R3 is hydrogen or C1-4 alkyl; and in the formula (IV), Y is chlorine, bromine, iodine or hydroxyl sulphonate.