This volume contains selected and peer-viewed papers presented at the 21st Chinese Materials Conference 2020(CMC2020) held online in Beijing, China, Nov. 17-22. 2020. The Chinese Materials Conference (CMC) is the most important serial conference of the Chinese Materials Research Society (C-MRS) and is held each year since the early 1990s. Chinese Materials Conference 2020 had 42 Symposia covering four fields of energy and environmental materials, advanced functional materials, high-performance structural materials, and design, preparation, and characterization of materials. This book will be useful and interesting for many engineers and researchers engaged in materials areas.