Objective To explore the feasibility and significance of using ventilated technology of oxygen after unchaining in assistant breathing equipment cycled with mixed gases of helium and oxygen.Methods After giving out the relative increment matrix for keeping the system steady,the paper introduces the detail methods for the control of oxygen concentration after unchaining coupling in assistant breathing equipment cycled with mixed gases of helium and oxygen.Results It shows that the control of oxygen concentration after unchaining coupling is a vital technology in assistant breathing equipment cycled with mixed gases of helium and oxygen.