Non-line-of-sight imaging can reconstruct images of scenes outside the line-of-sight. Different from traditional imaging, it imports the indirect signal returned from the hidden scene into the reconstruction algorithm to realize the reconstruction of the target scene, which is important in the fields of national defense, biomedicine, automatic driving, aerospace, and post-disaster search and rescue. This paper summarizes the research progresses of non-line-of-sight imaging technology, and introduces three non-line-of-sight imaging modes, including non-line-of-sight imaging based on time-of-flight, and non-line-of-sight imaging based on coherent information (including speckle pattern and spatial coherence methods), and non-line-of-sight imaging based on intensity information. Focusing on the characteristics and limitations of hardware parameters, reconstruction algorithms, reconstruction time, and image resolution of coherent information and intensity information imaging modes, the development trend of non-line-of-sight imaging is analyzed and discussed.