An OSP surface treatment package substrate forming milling method comprises the steps of finishing spliced semi-finishing product manufacture and performing electrical testing; baking spliced plates having passed the electrical testing; and performing sand blasting treatment on the baked spliced plates, and adopting emery and diatomaceous earth preferably for sand blasting treatment; performing OSP surface treatment so as to obtain an OSP surface treatment layer on the surface of a copper conductor; pasting adhesive tape to two sides of the spliced plates having undergone OSP surface treatment; performing milling treatment on the spliced plates where the adhesive tape adheres so as to obtain package substrate unit plate finished products covered with the adhesive tape; and stripping the adhesive tape on the package substrate unit plate finished products to obtain the package substrate unit plate finished products.