Traditional cigarette products have been used for hundreds of years. Although cigarette products have been favored by a considerable number of people, the potential hazards caused by smoking have also been paid a great deal of attention. Under these circumstances, governments have launched a series of policies and regulations to control the use of tobacco. With people paying more and more attention to their health, smoking cessation has been widely considered and accepted by the public. On the other hand, tobacco products are now being developed with greater diversification, and can be smokeless. One important form of new tobacco product, E-cigarette products, have been developed, and have quickly dominated the market share. E-cigarettes don’t burn or produce smoke and don’t contain solid particles or tar, while traditional smoke produces these harmful chemicals. Therefore, E-cigarettes are often considered to be safe, and are allowed to be used in public places in some countries and regions. Since the emergence of E-cigarettes, a number of scientists have done a lot of research to investigate their safety. Nevertheless, there is still no specific conclusion. The variation in the classification and control policies relating to the sale and production of E-cigarettes in different countries makes it more difficult to evaluate their safety. Although E-cigarettes only entered the market a short time ago, their characteristics of being both smokeless and relatively healthy for the environment and for health have led them to be quickly accepted and consumed by the public. At present, the main form of E-cigarette is the renewable liquid type. Due to its being fashionable, economical and practical, this is still the future focus of E-cigarettes in the next decades. Furthermore, different amounts of nicotine are added and used in E-cigarettes in various countries, which counteracts the principles of nicotine replacement therapy advocated by the WHO. Actually, there is no solid evidence showing that smoking cessation could be achieved by using E-cigarettes.