The investigation on the leaves of Morus alba L. was carried out to find the relationship of the constituents and the pharmacological activities. The isolation and purification were performed by various chromatographies such as silica gel, Sephadex LH-20, RP-C18 column chromatography and so on. Further detailed investigation on the fraction of the ethanol extract of leaves of Morus alba yielded four Diels-Alder type adducts mulberrofuran F1 (1), mulberrofuran F (2), chalcomoracin (3), kuwanon J (4), together with two chalcones morachalcone A (5), isobavachalcone (6), and three flavones norartocarpetin (7), kuwanon C (8), 6-geranylapigenin (9). Their structures were elucidated by the spectral analysis such as NMR, MS etc. Compounds 1, 6 were isolated from this plant for the first time, compounds 4-5, 7-9 were isolated from the leaves of Morus alba L. for the first time, among which 1 was a new compound. Compounds 1-5 were evaluated for the cytotoxicity against A549, Be17402, BGC823, HCT-8 and A2780 cell lines in vitro by MTT method, but only compounds 1-3 showed cytotoxicity against several human cancer cell lines.