Abstract: The CCDC 2021 continues to attract broad interest throughout the world, with 1576 submissions and acceptance of 1322 papers.This reflects the increased interest in our field, and creates a difficult workload in evaluating the papers and organizing a cohesive program.We owe great thanks to our International Advisory Committee.We were fortunate to have an exceptional International Program Committee (IPC) that sorted through the evaluations and integrated the individual submissions into the final technical program described in this volume.We also want to thank our Organizing Committee for their invaluable assistance in arranging the diverse offerings at the conference, from registration and local arrangements to technical programs.Last but not least, we would like to express our appreciation to the support from Northeastern University, China.The International Program Committee (IPC) has assembled a comprehensive technical program that covers a broad spectrum of topics in Control and Decision, Automation, Robotics and Emerging Technologies.The CCDC 2021 technical program begins on Saturday, 22 May, ends on Monday, 24 May, and comprises 103 sessions.Among the 103 technical sessions, there are 94 regular sessions, 9 interactive sessions.We thank the authors, keynote/distinguished lecturers, invited session organizers and session chairs for their tremendous contributions towards a top-quality program.