The invention discloses a preparation method of a narrow ridge semiconductor appliance; the preparation method includes steps of performing epitaxial growth and forming a semiconductor epitaxial piece; orderly forming a silicon dioxide mask film and a first photoresist mask film on the semiconductor epitaxial piece, and photoetching and forming a periodic first window; etching and removing the silicon dioxide mask film and a part of epitaxial layer of a first window zone by a dry method, and forming a narrow ridge structure; forming a second photoresist mask film on the upper surface of the formed narrow ridge structure, photoetching and forming a ridge type window; removing the rest silicon dioxide mask film out of the first window by selective corrosion fluid, and completing the appliance preparation. When the selective corrosion fluid is applied to remove the residual silicon dioxide on the surface of the ridge type waveguide structure, the selective corrosion fluid is only contacted with the residual silicon dioxide and the second photoresist mask film, thereby avoiding the dropping of the ridge structure from the main body in the process of corroding and removing the silicon dioxide; the prepared appliance performance and yield are high, and good light output can be realized.