Cancer can cause anemia. Cancer-related anemia is a common clinical manifestation of cancer, and the causes of anemia caused by cancer can be broadly classified into the following categories: a. Nutritional deficiency anemia, cancer patients will have decreased appetite and reduced food intake, resulting in malnutrition. Important raw materials for hematopoiesis, such as iron, vitamins and folic acid, must be taken from food, and less food will cause anemia due to lack of raw materials for hematopoiesis. Bleeding may occur in cancer patients. Acute massive bleeding may lead to hemorrhagic anemia, while chronic slow bleeding may cause loss of iron, an important hematopoietic raw material, which, together with reduced intake from food, will lead to iron deficiency anemia. Third, inhibition of hematopoietic function. After chemotherapy or metastasis of cancer cells to the bone marrow, cancer patients will obviously inhibit the normal hematopoietic function of the bone marrow, which will lead to anemia. In conclusion, cancer-related anemia is a common manifestation. Correcting anemia in cancer patients is not only helpful to prolong patients’ life span, but also important to improve the treatment effect.