Abstract: The circadian clock is an endogenous and self-sustaining timing mechanism that evolved to track daily rhythms and allow plants to prepare for predictable and recurring environmental changes, ultimately enhancing fitness and adaptation. The circadian clock plays a vital role in plant growth and development as well as pest and pathogen resistance. Pathogen and pest have different attacking capacity at different time. The circadian clock enables plants to anticipate the time of pathogen and pest attacks and promote the defence responses at the most effective time of the day. The circadian gating responses can increase resistance without substantial energy consumption. On the other hand, the changes in the level of phytohormones, reactive oxygen species (ROS) and ion homeostasis caused by biotic stresses are involved in clock resetting. Studying the correlation between circadian clock and immunity will increase plant pathogen resistance and reduce pesticides usage which would have a great agronomic impact on future crop breeding. Here we review the recent research on the interaction between the circadian clock and plant immunity, and highlight new avenues for future research.