The invention discloses a coumarin-based sulphonate photo-acid generator (photo-generated acid) and a preparation method therefor. The photo-generated acid is obtained by an esterification reaction between a coumarin compound including hydroxyl, and sulfonyl chloride. The photo-generated acid can produce acidic materials under certain ultraviolet lights; and photoresist prepared from the photo-generated acid provided by the invention can be developed under ultraviolet lights, and has the characteristics of high activity and high precision.