An ion mobility spectrometer comprising a continuously operable gas purification device, the continuously operable gas purification device comprising: a housing provided with a cylinder cavity ; a dry gas supply unit ; a rotating barrier arranged in a radial direction of the cylinder cavity to divide the cylinder cavity into a baking cavity and a working cavity ; and a rotating mechanism , wherein the housing is provided with a dry gas inlet , a dry gas outlet , a sample gas inlet and a sample gas outlet , both the dry gas inlet and the dry gas outlet are communicated with the baking cavity , while both the sample gas inlet and the sample gas outlet are communicated with the working cavity , wherein the dry gas supply unit is connected with the dry gas inlet for a dry gas supply to the dry gas inlet , wherein the baking cavity is provided with a heating unit correspondingly, and the rotating mechanism is provided at a central position of the cylinder cavity and is connected with the rotating barrier for rotating the rotating barrier at intervals, wherein the gas purification device further comprises two desiccant boxes filled with desiccants, the two desiccant boxes provided in the baking cavity and the working cavity respectively, wherein the two desiccant boxes each has a semi-cylindrical shape and is made of a closed structure, and wherein mesh holes corresponding to the sample gas inlet and the sample gas outlet are provided on a side wall of the desiccant box provided in the working cavity , and mesh holes corresponding to the dry gas inlet and the dry gas outlet are provided on a side wall of the desiccant box provided in the baking cavity . a housing provided with a cylinder cavity ; a dry gas supply unit ; a rotating barrier arranged in a radial direction of the cylinder cavity to divide the cylinder cavity into a baking cavity and a working cavity ; and a rotating mechanism , wherein the housing is provided with a dry gas inlet , a dry gas outlet , a sample gas inlet and a sample gas outlet , both the dry gas inlet and the dry gas outlet are communicated with the baking cavity , while both the sample gas inlet and the sample gas outlet are communicated with the working cavity , wherein the dry gas supply unit is connected with the dry gas inlet for a dry gas supply to the dry gas inlet , wherein the baking cavity is provided with a heating unit correspondingly, and the rotating mechanism is provided at a central position of the cylinder cavity and is connected with the rotating barrier for rotating the rotating barrier at intervals, wherein the gas purification device further comprises two desiccant boxes filled with desiccants, the two desiccant boxes provided in the baking cavity and the working cavity respectively, wherein the two desiccant boxes each has a semi-cylindrical shape and is made of a closed structure, and wherein mesh holes corresponding to the sample gas inlet and the sample gas outlet are provided on a side wall of the desiccant box provided in the working cavity , and mesh holes corresponding to the dry gas inlet and the dry gas outlet are provided on a side wall of the desiccant box provided in the baking cavity . <EOS>