The invention discloses a preparation method capable of roughening the surface of a p-GaN layer of an LED. First, an N-GaN layer, a quantum well layer, a P-GaN layer and an undoped roughening GaN layer grow on a semi-conductor substrate in sequence, second, ICP or ion dry etching are adopted to etch the undoped roughening GaN layer so that the shape of the roughening surface of the undoped roughening GaN layer is transmitted to the p-GaN layer, thus causing the surface of the P-GaN layer to be roughened. Compared with the prior art, the preparation method is easy to operate and has better roughening effect.