Abstract: OBJECTIVE To study the secondary metabolites of an endophytic fungus Aspergillus sp. TPXq isolated from Saussurea medusa. METHODS The strain was cultured in a large-scale by using the shaking incubator. The secondary metabolites were isolated by chromatography methods such as silica gel， Sephadex LH-20 columns， ODS flash column and HPLC， etc. The structures of these compounds were identified by their physico-chemical constants and the NMR data. RESULTS Eight Cyclodipeptides and one alkaloidwere seperated from secondary metabolites of an endophytic fungus Aspergillus sp. TPXq isolated were from Saussurea medusa.， and their stuctures were identified as 3-isobutylpyrrolopiperazine-2，5-dione (Ⅰ)，3-isopropyl-pyrrolopiperazine-2，5-dione (Ⅱ)， 3-seco-butyl-pyrrolopiperazine-2，5-dione (Ⅲ)， 3-benzyl-pyrrolopiperazine-2，5-dione (Ⅳ)， 3-benzyl-6-(p-hydroxy benzyl)piperazine-2，5-dione (Ⅴ)， 3，6-dimethylpiperazine-2，5-dione (Ⅵ)， 3-isobutyl-6-isopropylpiperazine-2，5-dione (Ⅶ)， 3-isobutyl-6-benzylpiperazine-2，5-dione (Ⅷ)， Chaetominine (Ⅸ)， by analysis of physiochemical and NMR data. CONCLUSION Among them， compounds Ⅳ~Ⅷ were isolated from Alterraria.sp for the first time. Compounds Ⅸ showed significant cytotoxic activity against A549 and MCF-7 tumor cells， the IC₅₀ values are 0.18μg/mL and 0.89μg/mL， respectively. However， compoundsⅠ~Ⅷ exhibited very weak cytotoxicity (>50μg/mL) against these cell lines.