It is usually recommended to choose a mercury thermometer for measuring body temperature, which is more accurate than an electronic thermometer and will avoid many errors. Mercury thermometers are used to measure deep body temperature, anal, axillary and oral temperatures, and are more accurate than electronic thermometers and are rarely affected by fluctuations in the external environment. When electronic thermometers measure forehead and ear temperatures, they are subject to fluctuations in the temperature of the external environment, and for children, when measuring forehead and ear temperatures, they can also cause fluctuations and effects on body temperature due to uncooperativeness and changes in body position. However, when the mercury thermometer measures the deep body temperature, the anal temperature and axillary temperature are relatively accurate and will rarely be affected by the external environment and the patient’s lack of cooperation.