Targeted drugs are drugs that patients and doctors want to target only malignant tumor cells, and these drugs try not to affect normal cells. With the development of molecular detection technology, there are ways to detect malignant genes that are detrimental to health and block them through molecular technology and monoclonal antibody technology, so as to achieve the purpose of tumor suppression or killing tumor cells without damaging normal cells, which is what we understand as selective targeted therapy drugs. This is what we understand as selective targeted therapy. Molecular blockade is molecular targeted therapy, which is a technique often referred to as gene therapy. Chemotherapy is still the main and most commonly used treatment for malignant tumors, which solves many patients’ treatment problems, but also brings some adverse effects of treatment. Targeted therapy is based on the expression of the patient’s genes or receptors to selectively administer drugs, the major difference is that it is more selective, so the efficacy is better, and the toxicity will be lower. Chemotherapy: Chemotherapy refers to the use of drugs to treat the disease. Surgery and radiation therapy kill cancer cells in specific areas, while chemotherapy works on the whole body. Chemotherapy can destroy cancer cells that have spread to various parts of the body. Often several drugs are used in combination to enhance the effectiveness of the treatment. Combining several drugs with different effects can kill more cancer cells, as well as reduce the possibility of the body developing resistance to a specific drug. It can be taken orally; applied topically; injected, etc. It should be said that targeted therapy avoids the toxicity of some traditional cellular drugs, but the mechanism of action of any drug will block the normal transmission of information to some cells in the body, which will also bring some corresponding adverse effects. Targeted therapy is to target a certain kind of cancer cells, or a certain protein or a certain molecule of cancer cells, which can distinguish friend from foe and kill tumor cells with less impact on healthy cells. The introduction of molecular targeted drugs will change the way of thinking and behavior of our clinical treatment, but now almost all molecular targeted drugs have to be based on the standard chemotherapy or can further improve the efficacy after chemotherapy, so its introduction is to improve the efficacy based on chemotherapy, not to replace the traditional chemotherapy. The molecular targeted drugs mentioned so far for breast cancer mainly target Her-2, the most mature and classical one is Herceptin (trastuzumab) which targets Her-2. The earliest study showed that Herceptin alone could achieve clinical efficacy in patients with ineffective chemotherapy, while subsequent studies proved that adding Herceptin to standard chemotherapy could further improve the efficacy, and the latest study results showed that The addition of Herceptin to chemotherapy for post-surgical patients with Her-2 overexpression (HER-2 transitional expression accounts for approximately 25% of breast cancers) can further improve the outcome of these patients, thus making a major breakthrough in the history of breast cancer, that is, the addition of a molecularly targeted drug with a different mechanism of action to previous chemotherapy can definitively improve the patient’s prognosis.