This study explores application of upcycling design methods in structural transformation of second-hand denim clothing, aiming to achieve sustainable design objectives. By drawing inspiration from Liu Qing's research methods in the field of circular utilization of denim clothing, this study collected and analyzed cases of structural transformation of used denim clothing from 2020 to 2023. It summarized structural transformation design methods for used denim clothing. Through the development of design works, this study aims to find out the best upgrading and renovation design strategy by applying the method of structural renovation design. This study aims to support the development of a sustainable fashion industry and promote recycling and upcycling of discarded clothing fabrics, thereby reducing resource waste and environmental impact.