With the development of science and technology, CT has become a routine examination in people’s daily visits to the doctor. Some people mistakenly believe that as long as a CT examination, any disease can be checked clearly. In fact, CT examination is not everything, the abuse of CT can even cause cancer. Recently, the U.S. Department of Health published a biennial report on carcinogens, the report for the first time X-rays included in the new 17 kinds of carcinogens. Studies have confirmed that exposure to X-rays can lead to the development of a variety of tumors, including leukemia, thyroid, breast, and lung cancers, as well as potentially tumors of the salivary glands, stomach, colon, bladder, ovaries, central nervous system, and skin. The risk of cancer depends to some extent on the age at the time of exposure; overexposure in childhood is not unrelated to an increase in leukemia and thyroid cancer, in the childbearing years there is an increased risk of breast cancer, and in later life there may be an increased chance of lung cancer. Clinically, although CT examination only accounts for 5% of X-ray examination, it accounts for 1/3 to 2/3 of the total radiation exposure of medical X-ray examination, of which diagnostic X-ray examination is particularly high and rising, especially the application of multi-phase spiral CT scanning technology (arterial phase, venous phase, delayed phase), the patient’s exposure to radiation has increased exponentially, and the chances of damaging their health and inducing cancers have also increased significantly. Especially children are more sensitive to X-rays than adults, and are more likely to be victimized. In recent years, U.S. scholars estimate that about 500 children under the age of 15 in the U.S. may be directly caused by CT scans for cancer, and the above figures are worrisome. The harm of CT examination to the human body is that the examinee is subjected to a larger dose of x-ray radiation. Domestic and foreign studies show that different types of CT machines for head scanning, the patient’s maximum body surface dose can reach an average of 36.6-70.0 MGY (3.66-7.00 roentgen), second only to the x-ray machine cardiac catheterization and gastrointestinal imaging, is a conventional x-ray chest X-ray or physical examination of the 2.8-11 times. CT scanning of the skin of the examined person the maximum absorbed dose can be as high as 560 MGY (56 roentgen), generally up to 60 MGY (6 roentgen), the maximum absorbed dose can be as high as 560 MGY (56 roentgen). Generally up to 60 MGY (6 roentgen) or so; abdominal CT examination of the radiation dose for the abdominal plain film 8 times; women for abdominal or pelvic CT examination, the uterus is irradiated dose than conventional x-ray diagnosis were 9 to 12 times higher, and the bone marrow is irradiated dose than the conventional x-ray were 16 to 23 times higher. The International Commission on Radiological Protection (ICRP) study confirmed that a CT whole body scanning physical examination will increase the risk of radiation-induced cancer of the examinee by about 8%. Radiation cancer and hereditary diseases are dose linear without threshold, that is to say, the more irradiated, the greater the likelihood of lethal cancer and hereditary diseases. At present, the abuse of CT examination phenomenon is common, the patient has a slight problem, that is, as a CT examination, some people even check several times in a month, which not only causes economic waste, and may cause radiation damage. Therefore, whether medical personnel or the people, should learn a little knowledge of radiation protection. Should strictly grasp the indications for CT examination, can use non-radiation methods (such as ultrasound) on the use of non-radiation methods, can be resolved by filming the CT examination is not necessary. Especially pay attention to women of childbearing age, pregnant women, infants and young children should try to avoid CT examination. Prevention is better than cure to minimize the harm caused by radiation to human beings.