The invention discloses a manufacturing process of large-area thick GEM. The manufacturing process comprises the steps of solder mask covering, laser windowing, insulating ring machining, through hole forming, solder mask removing and the like. The laser drilling mode and the dual positioning technology of laser drilling windowing and laser drilling through hole forming are adopted for machining the thick GEM. The manufacturing process of the large-area thick GEM has the advantages of being low in cost, high in machining precision and production efficiency and the like.