Terahertz focal plane array imaging is one of the most promising technology that has the advantages of high frame rate, staring imaging and real aperture imaging. As the core component in the terahertz focal plane imaging system, the terahertz focal plane array determines the sensitivity and resolution of the system. Firstly, the basic concepts of terahertz focal plane array is illustrated, including the system principle, typical architecture and pixel-level terahertz detector. Secondly, state-of-the-art of the terahertz focal plane array in directly-detection mode and mixing mode is presented respectively. Finally, critical technologies and development trends are summarized.