Two phenanthraquinones were isolated from the stems of Dendrobium moniliforme. They were identified by interpretation of spectral data as 2,6-dimethoxy-1,4,5,8-phenanthradiquinone and 5-hydroxy-3,7-dimethoxy-1,4-phenanthraquinone, named moniliformin (1) and denbinobin (2), respectively. This is the first report of compound 1, which possesses a novel 1,4,5,8-diquinone moiety in the phenanthraquinone skeleton. Compound 2 showed potent antiinflammatory effects in vitro.