In order to provide the reference for the further studies of Senecio laetus Edgew.,we dovote to investigate the chemical constituents from the whole plant of S. laetus.The silica gel,sephadex LH-20 and MCI gel were used for the isolation and the purification of compounds of the ethanol extract of S. laetus.Afterwards,the spectroscopic methods (¹H NMR,¹³C NMR) were used for the structural identification.The toxicity of two alkaloids 1 and 8 to hepatocytes were evaluated by MTT.And the antifungal activity was evaluated by agar plate drilling method.Eleven compounds were isolated from ethanol extract of the S. laetus and identified as othosenine (1),2-(4-O-β-D-glucopyranosyl) syringylpropane-1,3-diol (2),eleutheroside E (3),syringin (4),isorhamnetin-3-O-β-D-galactoside (5),quercetin-3-O-β-D-rhamnoside (6),stigmasta-5,22-dien-3β-ol (7),otosenine (8),isorhamnetin (9),quercetin (10),caffeoyl acetate (11).Compounds 1 and 2 were isolated for the first time from the genus Senecio,and compounds 3,4,7 and 11 were isolated from S. laetus firstly.Compound 1 is a new natural product and it′s NMR data was reported for the first time.The two pyrrolizidine alkaloids 1 and 8 showed no toxicity to normal hepatocytes cell line L-02.Compounds 1,7 and 8 showed excellent synergistic antibacterial effect on Candida albicans resistant strains when combined with fluconazole.