Abstract: Hybrid modeling is another research direction after parametric feature modeling in CAD systems．The conversion among wireframe model，surface model and solid model is the key technique of hybrid modeling．This paper introduces 1） Mapping from solid model to wireframe model and surface model respectively，2） Mapping from wireframe model to solid model and 3） Mapping from surface model to solid model．We also adopt the mapping algorithm into the design of IGES and STEP data interface．