Abstract: The effects of defoliation on the reflowering of four important autumn-flowering cultivars of tree peony(Paeonia suffruticosa) that growing under field conditions were studied.Resultsindicated that full defoliation was the key measure to autumn reflowering,and from late August to early September was the optimum defoliation time in Heze,Shandong Province.Chemical defoliators like abscisic acid(ABA) and ethephon could advance the flowering time of three autumn-flowering cultivars 2-6 days,and had a better effect on the reflowering quality and leaf development than artificial defoliation.The experiment also demonstrated that proper defoliation treatment after differentiation of the floral buds could induce tree peony to blossom in autumn,especially around 1st October,the National Day of China.