The invention relates to the technical field of combustion, in particular to a constant-volume combustion technology adopting a rotating valve to control opening and closing of a combustion chamber and a power system applying the constant-volume combustion technology. A device used for the constant-volume combustion technology comprises a base, a rotating shaft and the combustion chamber; a stepped through hole is formed in the base and matched with the rotating shaft in mounting; a gas inlet and a gas outlet are axially formed in the middle section of the top of the base and matched with a gas inlet and a gas outlet of the combustion chamber in mounting in a penetrated manner; a gas inlet passage and a gas outlet passage are axially formed in the rotating shaft; a gas inlet passage outlet groove is formed in the front section of the rotating shaft and communicated with the gas outlet passage and cooperates with the gas outlet in the top of the base to control opening and closing of the combustion chamber; a flow rectifying blade is arranged inside the combustion chamber. The constant-volume combustion technology has the advantages that the device can cooperate with the fixed base and the combustion chamber through the rotatable rotating shaft to control opening and closing of the combustion chamber so as to achieve constant-volume combustion, and the device is simple in structure and reliable in working.