<abstract> <p>In this work, the numerical simulation study of the hydrothermal flow and heat transfer process in the porous rock under 30 MPa pressure was developed. The flow and heat transfer characteristics of hydrothermal in rocks with different porosities are studied by changing the porosity of the rock. The simulation results show that the average flow velocity decreases and the average temperature increases when the porosity decreases. The velocity field and temperature field are coupled due to the nonlinear thermophysical properties of hydrothermal. The velocity field and temperature field have strongly interacted in the range of 400–450 ℃ and the effect of temperature on velocity is gradually diminishing outside the range. Most of the fluid will be "squeezed" into the crevice and the average velocity is almost three times the no-creviced case when a crevice is present. The existence of the crevice makes the total heat flux decrease from an overall perspective, and the crevice makes a large temperature gradient at the entrance and export of the crevice from a local perspective. These results provide theoretical support for the utilization of submarine hydrothermal fluid shallow circulation heat energy.</p> </abstract>