The present invention provides a liquid crystal display device and a method for manufacturing a light guide plate (LGP) positioning block thereof. The LGP positioning block (9) of the liquid crystal display device includes a positioning block body (91) and liquid (93) hermetically sealed in the positioning block body (91). The positioning block body (91) possesses elasticity. In a low temperature, the liquid (93) is condensed and expanded so as to enlarge the size of the positioning block body (91) to compensate the reduction of the size of a light guide plate (3) due to contraction caused by cooling; and in a high temperature, the elasticity of the positioning block body (91) absorbs the expansion of the size of the light guide plate (3) caused by heating. The LGP positioning block (9) of the liquid crystal display device is adjustable with the variation of the surrounding temperature so as to achieve effective positioning of the light guide plate (3) thereby providing high reliability of the liquid crystal display device and stable taste of displayed images.