Mass spectrometric studies on fragmentation patterns of 23 dibenzocyclooctadiene lignan compounds isolated from Schisandraceae plants, such as schisandra A (1), were carried out by using low and high-resolution mass spectrometric techniques and metastable ion analyses. The main mass spectral characteristics were summarized to provide a sound basis for further researches on Schisandraceae plants and for structural elucidation of similar new compounds.