Both ocean scientific drilling and exploration and development of gas hydrates are closely associated with well drilling, and both of them have the risks caused by hydrate formation and dissociation. Drilling fluid is treated as the "blood" of drilling engineering. Therefore, the drilling fluid system has been deeply studied by academia and industry, and different types of drilling fluids have been proposed in order to serve the scientific ocean drilling and the safe and efficient production of hydrates. This paper summarized the characteristics, risks of scientific ocean drilling and hydrate drilling and performance requirements of the drilling fluids as well as drilling fluids commonly used at home and abroad and their performance. This paper pointed out the existing problems in current research, and suggested further possible research directions of drilling fluids, so as to promote the commercial development of hydrate and serve ocean scientific drilling.