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 me-tabolites 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.RE-SULTS 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 physio-chemical 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(>50μg/mL)against these cell lines.