The invention relates to a preparation method of N-amino-3-azabicyalo [3.3.0] octane serving as a gliclazide side chain. The gliclazide side chain is obtained by carrying out one-step hydrogenation reduction on N-cyclopentyl amine imide through a transition metal atom-modified ruthenium-carbon catalyst. The activity of the modified ruthenium-carbon catalyst used in the method is obviously higher than that of an existing commercial ruthenium-carbon catalyst, so that the imide hydrogenation reaction which is hard to realize in the N-cyclopentyl amine imide can be carried out successfully. The preparation method of the gliclazide side chain is safe, efficient, high in yield and simple for posttreatment; the catalyst can be cyclically used indiscriminately, so that the production cost is substantially reduced, and green synthesis is basically realized; no waste water and no waste slag are produced; and the preparation method is particularly suitable for large-scale industrial production. The invention further relates to a production method of gliclazide, which has the advantages of short synthesis path, high yield, low preparation cost and the like.