Abstract: This paper discusses on the model design of a swirl tunnel containing a barrage, and depicts the flow state and hydraulic characteristics of the swirl tunnel. The flow state is obviously influenced by the barrage, the flow state of the swirl tunnel has two basic flow patterns: one is incomplete rotational flow, the other is complete rotational flow. The discharging capacity is controlled by a rotary flow generator and the barrage size, the influence of the barrage aperture on discharge is obvious, but the effect of the barrage position on discharge is not distinct. In consideration of the influence of the barrage, the form of the discharge formula may be not changed. The relationship between the barrage influence coefficient ξ and the d/D is an approximate linear relationship. The barrage obviously influences the ventilating state: in the same position with different barrages, the bigger the barrage aperture, the larger the ventilating amount; in the different positions with a same barrage,the longer the barrage position toward downstream, the smaller the ventilating amount.