Sketching is a natural and effective way to capture designer's brainstorms ideas. This paper presents a sketch-based graphics input system for conceptual design (SketchGIS), which is mainly based on online graphic recognition and dynamic user modeling. Online graphic recognition can discover latent primitive shapes among user-drawn strokes and show the regularized shape on the screen immediately based on spatial-relation graph (SRG) representation and conditioned partial matching by shape preparing, feature recognition, shape filtering and regularization. Dynamic user modeling method is used to recognize and predict sketchy composite shapes before they are completely drawn for user adaptation, which is based on the SVM-based incremental active learning method and the incremental decision tree induction method. Experiments show that the proposed method in this paper can yield good recognition precision, and the prototype system proposed provides fine user interaction effect, especially for UML diagramming.