Abstract: Marine cold seep, mainly formed by the seepage of natural gas hydrate, is a fluid composed mainly of water, hydrocarbons, hydrogen sulfide and or carbon dioxide. It is not only a sign of the existence of seabed gas hydrate, but also a substance closely related to greenhouse effect, marine ecological environment, cold seep biological community and other issues. The measurement of the fluid leakage flux and chemical composition of cold seep is of great significance for understanding the issues mentioned above. Compared with laboratory chemical analysis and numerical simulation, in-situ observation can ensure the reliability and authenticity of data. As a main mean, in-situ observation equipment of cold seep has developed rapidly in the past two decades. In this paper, according to its objectives and principles, the in-situ observation equipment of the cold seep is divided into three types: the in-situ observation equipment for the leakage gas flux of the cold seep, the in-situ observation equipment for the leakage liquid flux of the cold seep and the in-situ observation equipment for the chemical composition of the seepage fluid of the cold seep. The development of in-situ observation equipment for cold seep at home and abroad is summarized in this paper from the aspects of design significance and working principle. And the advantages, limitations and application range of the equipment are discussed. In the end, the future development direction of the in-situ observation equipment for the cold seep is prospected.