The invention discloses a wide-spectrum medium short wave infrared window for detector/Dewar packaging and welding and a preparation process. The window takes silicon as the substrate material. The edges and the side of one surface of the window are plated with gold films in certain thickness, with a nanoscale nickel-chromium layer as the bonding layer. The gold films are called metalization layer, and the edges and the side are used for detector/Dewar packaging and welding. The middle areas of the surface and the other surface are plated with wide-spectrum medium short wave infrared antireflection films with multilayer film structure and alternate high/low refractive indexes, wherein the antireflection films take ZnS and YF3 as the materials with high/low refractive indexes and the equivalent layer adopts ZnS and Si. The antireflection films are plated by such specific processes as ion source assistance, appropriate substrate temperature, etc. The average transmissivity T of the window is more than 95% in the range of 1.2-4.8mu m and the water-vapor absorption peak commonly appearing on YF3 does not appear on the window in the range of 2.7-3.0mu m. The window is stable in performance and is suitable for the medium short wave infrared detectors/Dewar of the modern multi-spectrum space remote sensing instruments.