Abstract: Previous algorithms usually recognize orthographic drawings with the matching of point-line or solid projections.But loops in the drawings contain a lot of information about surfaces.In this paper,an efficient algorithm is proposed to rebuild polyhedral model by constructing its faces using constraints and rules recognize from the shape structure and plane's projection.This algorithm can deal with polyhedral model only,however,with the introduction of face-region,it can be combined with model-oriented approach to handle shapes composed of quadric surfaces.