The invention discloses a nucleic acid nano structure for carrying antitumor drugs, a preparation method and applications thereof. The nucleic acid nano structure is a random two-dimensional and / or three-dimensional nano structure constructed through a DNA origami technology. The nucleic acid nano structure is obtained through self-assembly between a scaffold chain and a staple chain for auxiliary folding, wherein the scaffold chain and the stable chain are hybridized according to the base paring principle. The provided nucleic acid nano structure taken as the carrier of antitumor drugs can guarantee the antitumor activity of the carried antitumor drugs, and further improves the targeting property of the antitumor drugs. Thus the antitumor drugs can be enriched in the tumor tissues, and the overall toxicity due to the non-specificity of the antitumor drugs is greatly reduced. Furthermore, the preparation method has the advantages of simple technology, low cost, convenience, and easy application.