To investigate the non-alkaloidal chemical constituents of the stems and leaves of Melodinus suaveolens and their antibacterial activities. Compounds were isolated and purified by repeated silica gel, Sephadex LH-20, RP18, and preparative HPLC. Their structures were elucidated by comparison with published spectroscopic data, as well as on the basis of extensive spectroscopic analysis. The antibacterial screening assays were performed by the dilution method. Fourteen compounds were isolated, and identified as lycopersene(1), betulinic aldehyde(2), 3β-acetoxy-22,23,24,25,26,27-hexanordammaran-20-one(3), 3a-acetyl-2, 3, 5-trimethyl-7ahydroxy-5-(4,8,12-trimethyl-tridecanyl)-1,3a,5,6,7,7a-hexahydro-4-oxainden-1-one(4), 3β-hydroxy-28-norlup-20(29)-ene-17β-hydroperoxide(5), 3β-hydroxy-28-norlup-20(29)-ene-17α-hydroperoxide(6), β-sitosterol(7), 28-nor-urs-12-ene-3β, 17β-diol(8), α-amyrin(9), ergosta-4,6,8(14),22-tetraen-3-one(10), 3β-hydroxy-urs-11-en-28,13β-olide(11), betulin(12), obtusalin(13), and ursolic acid(14). Among the isolates, compounds 1, 2, 6, 8, 10, and 14 showed potent antibacterial activities against the four bacteria. This is the first report of the antibacterial activity of the constituents of Melodinus suaveolens. To investigate the non-alkaloidal chemical constituents of the stems and leaves of Melodinus suaveolens and their antibacterial activities. Compounds were isolated and purified by repeated silica gel, Sephadex LH-20, RP18, and preparative HPLC. Their structures were elucidated by comparison with published Spectroscopic data, as well as on the basis of extensive spectroscopic analysis. The antibacterial screening assays were performed by the dilution method. Fourteen compounds were isolated, and identified as lycopersene (1), betulinic aldehyde (2) 23,24,25,26,27-hexanordammaran-20-one (3), 3a-acetyl-2,3,5-trimethyl- 7ahydroxy-5- (4,8,12-trimethyl-tridecanyl) 3-hydroxy-28-norlup-20 (29) -ene-17β-hydroperoxide (5) norlup-20 (29) -ene-17α-hydroperoxide (6), β-sitosterol (7), 28- nor-urs- 12-ene-3β, 17β- diol (8) -4,6,8 (14), 22-tetraen-3-one (10), 3β-hydroxy-urs-11-en-28,13β-olide Among the isolates, compounds 1, 2, 6, 8, 10, and 14 showed potent antibacterial activities against the four bacteria. This is the first report of the antibacterial activity of the constituents of Melodinus suaveolens.