This book presents the proceedings of the 2021 International Symposium on Automation, Mechanical and Design Engineering (SAMDE), held in Beijing, China, on 3-5 December 2021, and organized by the Hong Kong Society of Robotics and Automation (HKSRA). It gathers contributions by researchers from several countries on the following topics: digitalized development and use of sustainable products and manufacturing systems, artificial intelligence, automated reasoning, human-robot collaborative interaction, sensors and autonomous sensor systems, cyber-physical control systems, generative design including topology optimization, advanced simulation and modelling, intelligent automation, smart materials, materials processing and factories, and circular economy, etc. The book offers a source of information and inspiration for researchers seeking to improve their work and gather new ideas for future developments.