The topic of AI has become more and more discussed ever since the release of ChatGPT, as its astonishing intelligence has made humans to challenge the boundary. This vagueness then contributes to the emergence of discussions on the ethics of AI. Aiming to clarify the many current academic discussions on the ethics of artificial intelligence and to recognize different ethical perspectives, this study conducts a literature review of the research and discussions among different scholars on ethical issues in the application of artificial intelligence technologies. It is found that the current relevant discussion extends from a micro perspective emphasizing the individual to a macro perspective emphasizing the human race. Research advances on ethical issues in AI applications can be categorized into three levels: personal, social, and global. Among which, the individual level focuses on the ethical issues in algorithmic logic and user data management. The social level focuses on the social employment and public accountability systems. While the global level discusses intellectual property disputes and the social identity of AI robots. Finally, the author gave an evaluation of the gaps and challenges of studying AI ethics and emphasize the importance of addressing ethical issues in AI development and deployment. The paper aims to serve as information for scholars and policymakers, fostering ethical awareness in the AI research community and helping AI technologies to be developed and used responsibly.