A three-dimensional reconstruction method and device based on a monocular three-dimensional scanning system is provided. The method includes: a depth map of a measured object is collected by using the invisible structured light scanning component, and the depth map is converted into a three-dimensional data point set, and the three-dimensional data point set includes a plurality of three-dimensional points; a target light plane equation corresponding to a target three-dimensional point is determined in the plurality of three-dimensional points; the target three-dimensional point is projected onto a modulated multi-line stripe image, and a target stripe corresponding to the target light plane equation is determined in the modulated multi-line stripe image; and a three-dimensional point reconstructed by the target stripe, in a camera coordinate system is obtained according to the target light plane equation and center coordinates of the target stripe.