In this paper, Grid Method, which is usually used in finite element mesh generation, is now applied for rapid modeling of arbitrary polygon Grid Structure, and it's function is realized in SPASCAD (the software of space modeling)by the developing of program. The engineer only selects the beginning edges of polygons and determines orientation of Grid.The software can automatic forming the model of plate space frame.The basic element of plate space frame includes Square pyramid and Triangular pyramid. The software can greatly improve the engineer's efficiency, This work just is preliminary research for the Rapid modeling of irregular grids, structures, and more development is needed to be continue.