Abstract: A high-entropy austenitic stainless steel and a preparation method thereof are provided. The elemental composition of the stainless steels developed by the invention is as follows: Cr: 5-30%; Ni: 5-50%; Ti: 1-15%; Al: 1-15%; the rest are Fe and inevitable impurities; preferably, the composition is Cr: 5-19%; Ni: 5-29%; Ti: 6-15%; Al: 5-15%; the rest element is Fe. By adjusting the atomic ratio of each element, the nano-sized precipitates are generated as much as possible, and the strength is maximized while maintaining a high plasticity. The stainless steels provided by this invention have only five alloying components, a low manufacturing cost, and high-strength and high-plasticity. They can be widely used in many industrial fields such as aviation, aerospace, marine, and nuclear power with broad market prospects.