Abstract: Based on the State of the Art about sketch-based research works,we present an intelligent modeling system which combed sketching recognition with geometric constraint reasoning.It addresses the issue of exploiting the stepwise refinement process and fast editing functions typical of conceptual designing.Further aiming at the ambiguity of the sketching input,it makes use of adaptive constraint reasoning techniques for multi-input sketches by introducing a decision-tree structure for top-down designing,the 3D objects are finally created by analyzing a set of history information.We illustrate the implementation of the algorithm and highlight its efficiency and feasibility for its adoption within Sketch-based Modeling Systems(SBMS).