This paper describes the fundamental research of, and subsequent development of the fabrication techniques-hot forming and heat treatment procedures-used in the pressure hull of a Deep Submersible Research Vehicle (DSRV). 10Ni-8Co steel is selected for the pressure hull of DSRV to be operated under sea 6000 m in depth, that is a double quenched and tempered (aged) ultra high strength steel with 0.2% proof stress above 120kgf/mm². In the application of this material to the pressure hull with hot forming and heat treatment procedure, the most important and difficult aspect is the control of tempering (aging) temperature of a hemisphere component. From this point of view, basic properties of this material and hot forming and heat treatment conditions effective for hemisphere fabrication are obtained from the fundamental research. To develop the fabrication techniques, a half scale model of a hemisphere is fabricated and tested with satisfactory results.