An online real-time registration method for an incomplete three-dimensional scanning point cloud having a plane reference. The method comprises: S1, standard model preprocessing, which involves: inputting a standard model, and obtaining a plane primitive set in the standard model, and relevant geometric information of each primitive; S2, data preparation, which involves: inputting three-dimensional scanning point cloud model data, a standard model file and a standard model feature template file; S3, calling a RANSAC shape recognition algorithm for the three-dimensional scanning point cloud model data to recognize plane primitives in the data; S4, for each plane primitive of a three-dimensional scanning point cloud model, establishing lists paired with all plane primitives in the standard model; S5, establishing all three-plane primitive groups according to the plane primitives; and S6, performing registration calculation between a three-plane combination of the point cloud model and all corresponding possible three-plane combinations in the standard model, so as to obtain the optimal registration homogeneous coordinate transformation matrix. By means of the present invention, the registration of all pieces of point cloud data does not need to be taken into consideration, and only plane features in a standard model and in an actual point cloud model need to be taken into consideration for recognition and matching, so that the number of searching cycles is reduced, and the aim of acceleration is achieved.