Abstract: The research, technology validation and exercises of planetary defense have become a hot topic and real concern for the international community. General introduction to the international planetary defense exercises (PDE) mainly organized by the United States has been given with a focus on the recent representative 2019 PDE and 2021 PDE. Comparative analysis has been carried out about the exercise participants, scenarios, procedures, and results. Discussions on the related aspects and requirements of planetary defense, such as monitoring and warning, impact risk assessment and active defense strategy, have also been performed. Inspiration and recommendations for Chinese planetary defense actions and related exercises have been proposed.