Abstract: In recent years, Critical Illness Insurance in China has achieved remarkable development, but its system construction is relatively lagging, and the nature and applicable law of Critical Illness Insurance are still not solved, obstructing the sustainable development of the system. In China's insurance legal system, considering the difference between social insurance and commercial insurance, the social attribute of Critical Illness Insurance does not constitute its essential attribute. Therefore, it is better to be defined as a kind of commercial insurance. Since Insurance Law applies to Critical Illness Insurance, it is suggested that special provision of Critical Illness Insurance should be added in Insurance Law and that Critical Illness Insurance Regulation should be legislated to provide system basis for Critical Illness Insurance.