Abstract: Today's world is in a "great changeunseen in a century".This is a new,scientific and accurate study of the characteristics of the new era of the world by the Communist Party of China.The major judgement of "a great change unseen in a century" has profound ontological,epistemological,contradictory and historical base of Marxist philosophy.As a scientific world outlook and methodology,dialectical materialism and historical materialism of Marxist philosophy provide important cognitive guidance,methodological basis and practical wisdom for us to deeply understand and accurately grasp the deep essence and philosophical basis of the "great changes unseen in a century".

Key words: "great changes unseen in a century", ontology, epistemology, theory of contradiction, view of history, Marxist philosophy