The invention discloses an excavation slope rock information extraction and three-dimensional reconstruction method. The method mainly comprises the steps that three-dimensional laser scanning point cloud data of an excavation slope surface are acquired; structural surface geometrical information of a slope rock is extracted by a Ransac algorithm; a rock block formed by the structural surfaces is extracted by using space geometry, a Flood Fill algorithm and a coding classification method; and a rock three-dimensional digital model is reconstructed and calculation and statistics are performed on the rock volume and blockness distribution information. The rock block information of the excavation slope surface can be automatically extracted so that the degree of block development formed by cutting of the structural surfaces can be visually reflected, and the defects of time consumption and labor consumption of manual measurement can be overcome; and the degree of integrity of the rock can be evaluated according to the extracted statistical information of the rock so as to provide the basis for the support design of the excavation slope.