PetDB is one of the most important basic databases in earth science and marine science. It is also the flagship for seabed petrogeochemical databases, which benefits marine geologists. PetDB combines nearly all the data of rocks from ocean floor, including petrological, mineralogical and geochemical data for rocks, glass, minerals and inclusions. For geochemical data it often contains the major elements, trace elements and isotopic ratios. The data in the database is integrated, well organized, easy for quiry and download. This quite popular and widely used database for petrology of ocean floor#cod#x02014;PetDB, which can be treated as a BigData tool in petrology, including the ideas to design the database, use instructions as well as its features, is introduced to domestic colleagues. It is well hoped that more and more petrogeochemists will pay more attention to and take interest in the database construction and BigData analysis, which is quite helpful in discussing new issues and performing scientific research.