The present invention provides an ophthalmic gel and a preparation method thereof. The ophthalmic gel comprises: an antibiotic; a nanocarrier, wherein the nanocarrier is used to load the antibiotic; and a biodegradable matrix, wherein the biodegradable matrix is compatible with the nanocarrier to carry the nanocarrier. When the ophthalmic gel of the present invention is applied to the surface of the cornea and conjunctiva of the eyes, the biodegradable matrix is automatically degraded and the nanocarrier carried by the biodegradable matrix will slowly release the antibiotic, loaded in the nanocarrier, at an appropriate rate to overcome the high-frequency use of general ophthalmic drugs and easily caused blurred vision; the present invention further comprises an ophthalmic gel preparation method.