The invention discloses a silencing and denoising dovetail three-way elbow and an elbow silencing treatment method. The dovetail three-way elbow comprises an inlet, an inner chambered surface a, a bottom plate a, an outlet, an outer chambered surface a, a top plate a, a top plate b, an outer chambered surface b, a flange, a bottom plate b and an inner chambered surface b. The top plate a, the top plate b, the bottom plate a, the bottom plate b, the inner chambered surface a, the inner chambered surface b, the outer chambered surface a and the outer chambered surface b can all be divided into a high-noise zone, a middle-noise zone and a low-noise zone. Silencing materials are arranged on the surfaces, positioned in the elbow, of the high-noise zone and the middle-noise zone for different thicknesses. Silencing treatment is carried out in different noise zones by adopting different silencing materials, and each part needing to be treated can be specially and accurately treated, so that the silencing effect is effectively improved.