Full-waveform LiDAR systems have been developed owing to their superiority in terms of high precision and resolution. However, further improving the imaging speed and resolution continues to be a problem. In this study, we propose an optical orthogonal code division multiple access (OCDMA) coding and 3D imaging technique, and a non-scanning full-waveform LiDAR system is first demonstrated. Encoding, multiplexing, and decoding are the essential modules of the OCDMA LiDAR system, which use M detectors and N-bits code to achieve high-accuracy decomposition for ${\rm M} \times {\rm N}$M×N pixels. In this paper, a complete 3D imaging LiDAR system is introduced, and the implementation of encoding and decoding is also illustrated. To prove that the technology is scientific and effective, an imaging experiment is carried out. The experimental result indicates that a system with only four avalanche photodiodes (APDs) can achieve 256 pixels. Moreover, the vertical resolution is about 1.8 cm and the range resolution is 15 cm at the distance of 40 m.