The invention discloses a method for improving the insulation performance of glass windows and doors, which is used for transforming single-layer glass windows, doors and curtain walls of old buildings. The improved glass window or door comprises existing single-layer glass A, a window/door frame and sealant, wherein glass with an adhesive tape is adhered to the indoor side of the single-layer glass A, and comprises single-layer glass B and a thermal-insulation adhesive tape adhered to the periphery of the single-layer glass B; a plastic film is adhered to the glass B along the surface of the thermal-insulation adhesive tape; and the glass with the adhesive tape is matched with the shape of the single-layer glass A, is smaller than the door/window frame, and is arranged inside the door/window frame, and a gap H is reserved between the glass with the adhesive tape and the door/window frame. During construction, the plastic film is peeled off, the glass with the adhesive tape and the single-layer glass A are adhered together by means of the thermal-insulation adhesive tape, and the sealant is applied along the gap H. The method is used for transforming old single-layer thermal insulation doors, windows and curtain walls so as to improve the thermal-insulation and sound-insulation effects of the glass doors, windows and curtain walls, realizes automatic batch production of glass with an adhesive tape, and has easily guaranteed quality and high efficiency.