An intraoral three-dimensional scanning system with a monocular camera includes the monocular camera. A first mirror and a second mirror perpendicular to each other are provided between the monocular camera and an object to be measured. A bisector of an angle formed by the first mirror and the second mirror is perpendicular to a lens of the monocular camera, and reflecting surfaces of the first mirror and the second mirror face the lens. A third mirror is provided at a side of the first mirror away from the second mirror, and a fourth mirror is provided at a side of the mirror away from the first mirror. The first mirror, the second mirror, the third mirror and the fourth mirror are located in the same plane.