Recently, Unmanned Aerial Vehicle (UAV) cluster technology is developing rapidly, and UAV cluster is playing an increasingly important role in various fields due to their adaptability, cost control and synergy, and is being studied intensively in various countries around the world. UAV cluster task assignment is a prerequisite for UAV cluster to execute its tasks efficiently, therefore, it is important to study how to achieve UAV cluster task assignment efficiently. This paper analyzes the task types, constraints, and task assignment methods of UAV cluster execution tasks, and then summarizes the problems in UAV cluster task assignment based on the current research status of UAV cluster task assignment, in addition, points out the future development direction. This paper is a reference for future research related to UAV cluster task assignment.