Aspergillus fumigatus, a type of endophytic fungi from Erthrophleum fordii, was fermented with GPY culture medium. Fermented liquid and mycelium were extracted from fermented products after freezing and thawing treatment. After alcohol extraction, mycelium was extracted with ethyl acetate and n-butyl alcohol, respectively. According to the results of cytotoxity of tumor cells, ethyl acetate extracts were studied for their chemical constituents. Five diketopiperazine compounds were separated and purified with silica gel, MCI and Sephadex LH-20 column chromatography, reversed-phase chromatographic column and preparative HPLC, their structures were identified as cyclo- (R-Pro-R-Phe) (1), cyclo- (trans-4-OH-D-Pro-D-Phe) (2), cyclo- (R-Tyr-S-Ile) (3), cyclo-(R-Phe-S-Ile) (4), and cyclo-(R-Val-S-Tyr) (5) by using spectral methods.