With the development of chalcogenide photonic devices, there is an increasing demand for high-quality chalcogenide optical waveguides which are widely used in infrared sensors, all-optical signal processing and other fields, therefore, the preparation of high-quality chalcogenide optical waveguides has become one of the hot fields of chalcogenide photonics. In the preparation of chalcogenide optical waveguide, the preparation methods include ion implantation, wet etching, dry etching, stripping and so on. Among these methods, the dry etching for preparing chalcogenide waveguide is used widely. Especially in recent years, researchers have successfully prepared As₂S₃, As₂Se₃, Ge-Ga-Se and other chalcogenide optical waveguides by dry etching. However, due to attack of the chalcogenide films (especially As₂S₃ film) by the alkaline developer which is used in the dry etching, the preparating process of As₂S₃ ridge waveguide needs very precise design and the quality of the chalcogenide waveguide can be affected. To improve this situation, some researchers proposed adding protective layers to prevent the attack of the developer on the As₂S₃ film. Previous researchers have tried to introduce Bottom Anti-reflection Coating, Polypropyl Methyl Acrylate and SU-8 as protective layers. However, the addition of such protective layers will further make the preparation process of waveguides cumbersome. In this paper, it is found that AZ5214 photoresist will retain the residual film with a certain thickness which is attached to As₂S₃ film under a certain exposure dose and appropriate development time. Based on this, this paper proposes to use this residual film as a protective layer to prepare the As₂S₃ ridge waveguide by dry etching. This protective layer can prevent the attack of the developer on the As₂S₃ film, and also be removed by etching, which will simplify the pattern transfer process compared with other protective layers. In this paper, the as-deposited As₂S₃ films with a film thickness of about 1 μm were deposited by vacuum resistance evaporation onto silica wafers, and then were annealed in a vacuum oven. The root mean square roughness R_q of the annealed As₂S₃ films decrease from 0.853 nm to 0.501 nm, which displays the achievement of high-quitly film with smooth surface. After that, the AZ5214 positive photoresist was covered on the surface of these As₂S₃ film to produce waveguide patterns in exposure process and prevent the attack of the alkaline developer owing to the residue photoresist bottom film as a photoprotective layer in development process. In the exposure and development process, the preparation parameters of this photoprotective layer were explored experimentally, and show that under the condition of exposure dose of 200 mJ/cm² and development time of 45 s, the AZ5214 photoresist with thickness of about 2.1 μm could form the photoprotective layer with thickness of about 220 nm and the R_q of about 17 nm. On this basis, the As₂S₃ ridge waveguides with width of 3 μm and height of 800 nm were prepared by using reactive ion etching. However, due to the relatively low etching selection of argon gas, there was a certain undercut phenomenon during the etching process, resulting in a trapezoidal cross-section shape of the waveguide. In order to mitigate this influence, the etching parameter was optimized for obtaining the As₂S₃ ridge waveguide with good- morphology in this paper. In addition, the transmission loss of As₂S₃ ridge waveguide is approximately 0.74 dB/cm by adopting the cutting back method. These works show that the preparation of chalcogenide waveguide by using AZ5214 photoresist bottom film as a photoprotective layer simplifies the preparating process, and achieves good results, which will bring new ideas and preparation technologies for the preparation of high-quality chalcogenide photonic devices and promote the development of chalcogenide photonics.