With the help of principle of wind turbine diffuser and based on improving generation efficiency of impulse wave device,the paper designed a kind of variable angle deflector.When flow velocity is small, the deflector expand the impact force of internal initial current on impeller and increases the utilization ratio of wave; under condition of high flow velocity,the variable angle device can gradually reduce inlet area so as to avoid internal impeller overload.The paper extracted the influence factors of dome protection and applied RNG turbulent model to analyze three main factors,and selected level III waves flow velocity to calculate related numerical.The experiment methods validated its performance by making model. The test selected radius 0.5m impeller, inlet flow rate reaches 8.1m/s for 0.058m2, this case is not sufficient to start the impeller. The results indicated that the installation of variable angle dome has evident protective effects on the impeller.