Abstract: To operate the BOP and shut-in valves correctly in case of any blowout,this paper restates the principle and handle position of the valve based on the issues indicated in a literature review,including "Discussion on Handle Position of Three-position Four-way Directional Control Valve in Remote Control Console of Well Control System".Views and results in the article were verified individually,and the principle of hydraulic control and hydraulic line circulation process were thoroughly investigated.The hydraulic control was analyzed,and the pressure in control line was tested under different control modes.Then,the results of the two handle positions were compared.The results showed that the pressure ahead of the valve was maintained at 8.5-10.5 MPa as long as operation time was more than 1 second and the pressure in control line behind the valve dropped to about 0 MPa when the handle position switched from open or closed or to neutral,and as long as the handle position was in neutral,the BOP and hydraulic valves could be constantly locked at their appropriate positions,the pressure was maitained,and pipeline and BOP seals were protected.In addition,the temperature difference had no effect on the reliability and life of hydraulic lines. The research results showed that the handle of three-position four-way directional control valve should be kept at a neutral position during drilling.Leaving the BOP handle open and the hydraulic handle closed was dangerous for well control.The three-position four-way directional control valve used abroad is different from that in China regarding its principle,so it is not necessary to maintain the standby position.