The invention relates to the technical field of protective films, in particular to an arc-surface protective film bringing convenience to attachment and a preparing method of the arc-surface protective film. The arc-surface protective film is of an arc-surface structure and comprises a release film body, a composite base material layer, a mucilage layer and a separating film body, wherein the release film body, the composite base material layer, the mucilage layer and the separating film body are sequentially arranged from top to bottom. The upper surface and the lower surface of the composite base material layer are attached to the lower surface of the release film body and the upper surface of the mucilage layer respectively, and the lower surface of the mucilage layer is attached to the upper surface of the separating film body. As the arc-surface protective film is of the arc-surface structure, accurate alignment can be achieved for attachment so that attachment efficiency can be improved, and attachment quality can be guaranteed.