As a classic humanistic thinking, Marxism has an obvious difference from Christianity. While the former, a revolutionary theory about human emancipation, and a worldview of atheism, embodies the ideology of proletariate, the latter, being considered as the historical achievement of human religious faith and the creation theory of theism, covers up the valueconcept of bourgeoisie. But as far as the humanistic care is concerned, both have an intercommunity. In detail, both are common and interlinked in such aspects as the ideal society, the human welfare, the philanthropic spirit, the fair order and the free right. Based on this, and being established in the historical process of China' s construction of the harmonious society of the peopleoriented, this essay gives an emphasis on their mutualaid relationship in the aspects of humanistic thinking and humanistic care, which possesses a beyondneglect significance in practice. On the one hand, Marxist revolutionary pursue for the happy ideal of the present society can fill a void in Christian seeking for the distant paradise of human afterlife and renovate the feeble salvation by solid activity; and on the other hand, the human limited ability and humanistic faultiness, which are established by Christian original sin, can wake the Marxist in prudently holding human rationality for seeking ideal, preventing him from rash advance, and, by way of modest piety, makes a constant approach to the perfect ideal society, thus ensuring the realistic benefit of the people oriented, and guiding the pursue for the peopleoriented spirit. The principle of seeking common ground, cooperation and mutual aid can be thought as the concrete mode in humanistic thoughts by which Marxism and Christianity go ahead together, and also as the new measure of strengthening the construction of the harmonious society.