A polarization conversion mechanism for a touch screen display includes a crystal layer and a polarizing layer. The crystal layer includes a birefringent crystal for changing phase delay effect in accordance with the orientation of the crystal axis thereof. The polarizing layer includes at least one linear polarizer such that an incident light after hitting a display module of the display device reflects and emits out through the linear polarizer and the crystal layer sequentially as reflection light in form of circularly polarized light or elliptically polarized light. The assembly of the crystal layer and the layer are installed to the display device and/or touch screen display in such a manner that the assembly is located on the display module thereof.