The embodiment of the invention provides a liquid crystal display device and a preparation method thereof, belongs to the technical field of display, and can effectively enhance the efficiency and accuracy of detecting polarizer attachment. The liquid crystal display device comprises a color filter substrate, an array substrate, an upper polarizer and a lower polarizer, wherein the color filter substrate includes a first scale ruler and a second scale ruler; the array substrate includes a third scale ruler and a fourth scale ruler, both located in the non-display area; the first scale ruler is used for measuring the distance from at least one parallel first side of the upper polarizer to the edge of the adjacent color filter substrate; the second scale ruler is used for measuring the distance from at least one parallel second side of the upper polarizer to the edge of the adjacent color filter substrate; the third scale ruler is used for measuring the distance from at least one parallel third side of the lower polarizer to the edge of the adjacent array substrate; the fourth scale ruler is used for measuring the distance from at least one parallel fourth side of the lower polarizer to the edge of the adjacent array substrate.