The invention relates to the technical field of optical detection, and provides a non-contact detecting method and device for a curved-surface prism for solving the problems that an existing contact detecting method for a curved-surface prism easily damages the optical surface of the prism and is low in testing precision; and an existing non-contact detecting method is complicated in testing optical path, quantitative detection cannot be realized and the like. The detecting method comprises the following steps: 1) aligning an auto-collimation microscope with a sphericity interferometer; 2) placing a to-be-detected curved-surface prism between the auto-collimation microscope and the sphericity interferometer, and enabling the convex surface of the to-be-detected curved-surface prism to be positioned in front of the sphericity interferometer; and 3) detecting the convex surface of the to-be-detected curved-surface prism by the sphericity interferometer, and adjusting the to-be-detected curved-surface prism to realize auto-collimation of the convex surface of the to-be-detected curved-surface prism and a light beam of the sphericity interferometer; and then detecting the concave surface of the to-be-detected curved-surface prism by the auto-collimation microscope, and moving the auto-collimation microscope to realize auto-collimation between the auto-collimation microscope and theto-be-detected curved-surface prism. The relative movement amount of the auto-collimation microscope is the distance of the center of sphere of the to-be-detected curved-surface prism.