To study the chemical constituents of the medicinal plant Chloranthus multistachys Pei and their anti-tumor activity.The compounds were separated and purified by column chromatography such as silica gel,reverse phase column chromatography,Sephadex LH-20,preparative HPLC and other chromatographic separation methods.Their structures were identified by spectral analysis and comparison with the data in reported literatures.As aresult,nineteen compounds were isolated and their structures were identified as (12R)-labda-8(17),13E-dien-12,15,19-triol (1),oplodiol (2),lasianthuoactone A (3),ent-8(9)-pimarene-20-hydroxy-16-nor-15-oic acid (4),3α,15β-dihydroxy-ent-kaur-16-ene (5),inflexarabdonin J (6),fraxidin (7),6-hydroxy-7,8-dimethoxycoumarin (8),N(N′-benzoyl-S*-phenylalaninyl)-S*-phenylalaninol benzoate (9),N-benzoyl-L-phenylalaninol (10),(R)-N-(1′-methoxycarbonyl-2′-phenylethyl)-4-hydroxybenzamide (11),(E)-3-(benzo［d］［1,3］dioxol-5-yl)-N-phenethylacrylamide (12),flavokawain A (13),stigmast-4-ene-3β,6β-diol (14),β-sitosterol (15),cycloart-23-ene-3β,25diol (16),sobrerol (17),vallinic acid (18),cinnamic acid (19) respectively,based on the spectral data,among the compounds 3,12-18,the remaining compounds were isolated from this plant for the first time.The cytotoxic activities of compounds 1-19 on human breast cancer cell line MCF-7,human prostate cancer cell line DU-145 and human lung cancer cell line A549 in vitro were tested by MTT assay.The results showed that compounds 13,16 and 17 had a certain inhibitory effect on the growth of A549 cells.