The invention belongs to the field of pharmaceutical agents, relates to a polymer micelle lyophilized agent encapsulating an insoluble antitumor drug as well as a preparation method and an application thereof. The polymer micelle lyophilized agent is prepared by carrying out molecular self-assembly on a methoxy poly(ethylene glycol) 2000-polyester block copolymer to form micelles, and then encapsulating the insoluble antitumor drug in a hydrophobic core formed by the polyester. The lyophilized agent has high encapsulation rate, high drug loading and small particle size, can significantly improve the water solubility of the insoluble drug and result in passive targeting of more antitumor drugs to concentrate in the tumor tissues, thus improving an anti-tumor treatment effect and reducing the toxic and side effects of drugs, and can be used to prepare the drugs used for the treatment of lung cancer, intestinal cancer, mammary cancer, ovarian cancer, etc. The lyophilized agent can also be quickly dissolved and dispersed to form a transparent micellar solution after water for injection, normal saline solution and the like are added, and is used for the preparation of the drugs for treating primary intestinal cell carcinoma.