Single-pixel imaging aims to record the target scene information via a single element detector. For its high sensitivity and wide range of spectrum response, single-pixel imaging is attracting a lot of attentions. Based on the coded acquisition and decoded reconstruction of high dimensional optical signal, single-pixel imaging can meet the demanding requirements in some challenging cases. The research background of single-pixel imaging was firstly introduced, and its imaging principle and reconstruction algorithms were briefly described. Then, from the perspective of coding and decoding of optical information, the current researches and advanced technologies were systematically reviewed. Besides, the existing problems in single-pixel imaging, and its future extensions and potential applications were discussed.