Recently, non-line-of-sight imaging has been presented as a novel imaging technology that can expand the human field of vision. Its operation is based on time-of-flight detection technology, which can detect photons reflected from objects outside the field of view, thereby reconstructing the images of hidden targets using a reconstruction algorithm. This technology has significant application prospects in the fields of disaster relief, medical diagnosis, antiterrorism operations, and unmanned driving. The research status of active and passive non-line-of-sight imaging systems in recent years is briefly summarized, and their characteristics and development trends are analyzed for each imaging system. The paper also discusses some key issues that need to be addressed in the practical application of partial non-line-of-sight imaging technology along, along with prospects for the development of non-line-of-sight imaging technology.