E-cigarettes are harmful to health. E-cigarette is an electronic product that imitates cigarettes. Its appearance, taste and feeling are the same as cigarettes. It is a product that users can smoke after turning nicotine into steam through atomization and other means. The World Health Organization conducted a special study on e-cigarettes, and concluded that e-cigarettes are harmful to public health, not a means to quit smoking, and management must be strengthened to prevent harm to teenagers and non-smokers. Studies have shown that people may inhale other undiscovered toxic compounds except nicotine when using e-cigarettes. At the same time, e-cigarettes will also endanger the health of people around them like second-hand smoke. It will release inhalable liquid fine particles and ultrafine particles, nicotine and carcinogens into the room. Because e-cigarettes do not produce smoke, it is easy to mislead consumers into thinking that they are safe and healthy, which is a wrong cognition.