A device and a method for adjusting post-spacer height in production of liquid crystal displays (LCDs), and the device comprises a controller (11) and an extrusion panel (12), the controller (1) is configured to control the extrusion panel (12) to perform plastic deformation treatment; and the extrusion panel (12) is configured to perform plastic deformation treatment on post spacers on a substrate, of which a height is more than a predetermined height value, under the control of the controller (11) after a rubbing process and before a cell assembly process, so that the standard deviation of the post-spacer height on the substrate can fall in a range of the predetermined standard deviation required to be achieved by products. The device and the method can effectively improve the uniformity of the post-spacer height on the substrates.