The present invention provides a method for fabricating a flip chip semiconductor light-emitting device which includes a substrate and a semiconductor multi-layer structure. The method of the invention includes the steps of: (a) forming a semiconductor multi-layer structure on a first substrate; (b) flip-chip bonding the semiconductor multi-layer structure on a second substrate; (c) removing the first substrate, so as to expose a first surface of the semiconductor multi-layer structure; and (d) forming a plurality of protrusions, arranged periodically, on the first surface. Particularly, the protrusions comprise a first protrusion and a second protrusion adjacent to the first protrusion, the first protrusion and the second protrusion both having a peak, and the second surface having a bottom, wherein the ratio of the vertical distance between one of the peaks and the bottom and the horizontal distance between the two peaks is in between 0.01 and 10.