Major studying methods and their new development related to palaeo ocean dissolved oxygen are summarized and discussed. Studying methods discussed include bioturbation, sulfur/carbon ratio, degree of pyritization (DOP), sulfur and carbon isotopes, trace element, rare earth element (mainly cerium anomaly), organic geochemistry and palaeo ecology (mainly dissolved oxygen index). It is proposed that reestablishment of the paleo ocean dissolved oxygen will greatly benefit to understand paleo ocean current, paleo climate, bio events, and organic evolution, which will largely be relied on establishment of substitute markers for dissolved oxygen, knowledge of oxic environment and oxygen cycle of Earth science system.