Animal-testing is one the most popular controversial topics, and has been debating in many fields including ethic, right, science, etc. However, animal-testing have not just started in our generation, but it has been occurred since at least 500 BC. In former time, physician-scientists such as Aristotle, Herophilus, and Erasistratus used animal experiments to discover the functions of living creatures. Nowadays, in the United States, around 26 million animals are used every year in experiments for the purpose of science, medical treatment, safety and others. Nevertheless, many people argue that animal-testing is not a good idea because animals are not suitable for experiment, animal experiments are usually ineffective and harmful for human, and animal-testing is contrary to ethic. In contrast, many people support its existence, giving their three main reasons, which are animals are suitable in experiment, animal-testing is beneficial for both humans and animals, and killing animals is common.