The combustion instability has been an ubiquitous problem for more than a century, especially for the first-order tangential modes. In this mode, the heat transfer rates may be greatly enhanced, resulting in the deterioration of the propulsion performance and even severe physical damage of the injector face-plate. In this paper, the effect of the longitudinal baffled blades on the first-order tangential acoustic mode in a cylindrical chamber with the nozzle was theoretically and experimentally investigated. The longitudinal baffled blades were installed on the inner surface of the chamber. The linear analysis method was adopted. The theoretical results were in good agreement with the experimental results. The conclusion was that the longitudinal baffled blades can restrain the first-order acoustic instability of the combustion chamber. With the increase in the height and number of the baffle blade, the amplitude of the first-order tangential acoustic mode gradually decreased, while the amplitude of the other modes gradually increased. With the increase in the diameter of the nozzle outlet, the amplitudes of the first order tangential oscillation mode and the first-order tangential acoustic mode all decreased. However, they varied in a relatively small range. (C) 2019 Published by Elsevier Ltd.