The present invention provides a liquid crystal display substrate and a preparation method thereof, which belongs to the technical field of liquid crystal display and may solve the problem that vias in the existing liquid crystal display substrate will result in non-uniform thickness of an alignment layer and thus influence the display effect. The liquid crystal display substrate provided by the present invention comprises a plurality of display structures, and an alignment layer located above all the display structures, wherein at least some of the display structures are provided therein with vias, and at least some of the vias are surrounded by baffle walls that are located under the alignment layer.