The embodiment of the invention provides am optical masking plate and a preparation method for an The optical masking plate comprises a light permeable zone and a light shielding zone with appointed patterns, wherein the appointed patterns comprise unit patterns which can be spliced to form at least two patterns to be exposed. The optical masking plate can be adopted to prepare multiple differentoptical masking substrates, and the universality can be improved. The embodiment of the invention further provides a preparation method of the optical masking substrate based on the optical masking plate. The preparation method comprises the following steps: confirming unit patterns which can be spliced to form patterns to be exposed, and periodically exposing masking plates to be exposed on the basis of the unit patterns till patterns to be exposed are formed on the substrate to be exposed, thereby obtaining the optical masking substrate. By controlling exposure times, the optical masking substrate with multiple patterns to be exposed can be prepared, the production cost can be greatly reduced, and waste of production resources can be reduced.