Abstract: In this paper, deep-sea optical detection technology was reviewed to arouse the attention and support of the academic community and related fields to deep-sea optical detection and sensing technology. Marine sensors are functional devices capable of sensing, collecting, converting, transmitting, and processing various marine observation elements as indispensable “perceptual terminals” in the fields of marine environmental monitoring and underwater target detection, and occupy a key position in the marine detection and monitoring technology system. However, affected by the complexities of seawater media and underwater environment, traditional land measurement and sensing technologies are often difficult to be directly applied to underwater scenarios, which is particularly prominent in deep-sea extreme environments with greater measurement difficulty. At present, the detection and research of deep-sea extreme environments have become a frontier issue in marine sciences, and various adaptive sensing devices have been developed to meet the needs of deep-sea detection. Among them, new optical sensors mounted on underwater mobile platforms can efficiently monitor underwater gas characteristics and accurately perceive the seabed surface morphology, playing an increasingly important role in the new round of marine detection process. Focusing on the two major directions of underwater gas monitoring and terrain detection, we summarized systematically the basic principles of domestic and foreign marine optical sensing technologies, the characteristics of mainstream products, and their application status in deep-sea extreme environment detection, marine environmental monitoring, and other fields. Based on the needs of future deep-sea extreme environment detection and marine mineral resource exploration, we discussed the prospects of the development trends.