This paper tackles the challenge of autonomous target search using unmanned aerial vehicles (UAVs) in complex unknown environments.To fill the gap in systematic approaches for this task, we introduce Star-Searcher, an aerial system featuring specialized sensor suites, mapping, and planning modules to optimize searching.Path planning challenges due to increased inspection requirements are addressed through a hierarchical planner with a visibility-based viewpoint clustering method.This simplifies planning by breaking it into global and local sub-problems, ensuring efficient global and local path coverage in real-time.Furthermore, our global path planning employs a history-aware mechanism to reduce motion inconsistency from frequent map changes, significantly enhancing search efficiency.We conduct comparisons with state-of-the-art methods in both simulation and the real world, demonstrating shorter flight paths, reduced time, and higher target search completeness.Our approach will be open-sourced for community benefit 1 .