2021 International Conference on Smart City and Green Energy was held as a fully virtual conference during November 20-22. The conference was co-sponsored by IEEE PES, Zhejiang University and Zhejiang University of Technology. Accepted papers after peer review have been published by IEEE, and included into IEEE Xplore, which are available online now: https://ieeexplore.ieee.org/xpl/conhome/9654276/proceeding. We'd like to thank all the keynote speakers, including Prof. Juan Manuel Corchado Rodriguez, University of Salamanca, Spain ; Prof. Kazuya Takeda, Nagoya University, Japan; Prof. Lim Yun Seng, Universiti Tunku Abdul Rahman, Malaysia, the international program committees and reviewers who have put a lot of effort in paper review.