Abundant data and samples have been recovered by ocean drilling for studying the seafloor hydrothermal activity. On the basis of these data and samples, we have understood the seafloor hydrothermal circulation by studying the fluid-sediment/rock interaction, the heat and mass flux, the fluid flow, and the tectonics in control of seafloor hydrothermal activity. And we have got some knowledge about the characteristics of seafloor hydrothermal-origin petroleum, the architecture and constitute of seafloor hydrothermal products, and the relationship between the deep biosphere and the seafloor hydrothermal activity by analyzing these data and samples from the ocean drilling. In the future, more achievements of studying seafloor hydrothermal activity will be got by carrying out the Integrated Ocean Drilling Program.