Euryachins A (1) and B (2), a new type of tetracyclic diterpenoid named a euryamane type, were isolated from the branches of Eurya chinensis. Their structures were elucidated through extensive spectroscopic analysis with the absolute configuration of 1 determined by single crystal X-ray diffraction analysis. A biogenetic pathway was proposed to account for the formation of this new type of diterpenoid. Both 1 and 2 exhibited anti-inflammatory activities with potencies comparable to the positive control L-NMMA, as evaluated against NO production in LPS-stimulated RAW264.7 cells.