Compton camera (CC) is a new type gamma-ray imaging modality. Because CC has no mechanical collimation structure, it has unique advantages in detection efficiency compared with other gamma-ray imaging modalities. Due to these advantages, Compton camera system is well applied in many fields, such as astronomical observation, medical imaging, environmental radiation monitoring, proton therapy and so on. With the development of emerging detector technology and electronics technology, Compton camera systems have been continuously optimized from scintillator detectors to high-performance semiconductor detectors. Moreover, except for traditional dual-layer detector structure Compton camera, new structures have also been proposed, such as "separate" structure and "integrated" structure. In this paper, the imaging principle, reconstruction algorithm and key factors affecting the performance of Compton camera, as well as the latest development of Compton cameras worldwide, are investigated and summarized. The imaging angular resolution of state-of-the-art Compton cameras generally reaches several degrees, and the spatial resolution reaches the order of 1 mm.