The invention provides an etching method of an InGaP epitaxial layer. The InGaP epitaxial layer grows on a substrate; and the etching method comprises the steps of growing and forming a silicon-based thin film layer on the InGaP epitaxial layer by employing a chemical vapor deposition process; coating the silicon-based thin film layer with a photoresist to form a photoresist layer; etching a photoetching pattern on the photoresist layer by employing a photoetching technology; and etching a target pattern corresponding to the photoetching pattern on the silicon-based thin film layer in the photoetching pattern by employing a reactive ion etching technology; etching the InGaP epitaxial layer in the target pattern by using a mixed acid liquid of a concentrated hydrochloric acid and a phosphoric acid; and removing the remaining part of the photoresist layer. By the etching method, the side etching phenomenon can be effectively inhibited.