Precautions to be taken during breast cancer radiotherapy include local care, ensuring diet, paying attention to observation, maintaining mentality and so on. 1. Local care: breast cancer patients will cause damage to local skin during radiotherapy, patients should keep clothing loose, breathable and soft, so as to make the skin at the breast breathable and dry. Patients should avoid using toiletries containing chemical ingredients directly on the chemotherapy site and avoid local friction and stimulation. 2. Ensure diet: patients may have nausea, vomiting, diarrhea and other adverse reactions during radiotherapy, so they should pay attention to strengthening nutrition, consuming high-protein, low-fat and easy-to-digest food, and increasing water intake appropriately, so as to promote metabolism of the body and reduce the side effects. 3. Pay attention to observation: breast cancer patients should pay attention to observation during radiotherapy, and conduct regular blood tests to avoid bone marrow suppression. 4. Maintain mentality: before and after radiotherapy, psychological guidance should be given to the patients to reduce their nervousness and fear, so that they can maintain a peaceful mentality during the treatment process, which will help them recover. If breast cancer patients feel unwell during radiotherapy, they should go to hospital for treatment in time to avoid affecting the effect of radiotherapy.