This invention presents a method and a system that use rendering facets to conduct hybrid geometric modeling for three dimensional product design, wherein a geometry operation comprises the steps: mapping rendering facets to operating facets, creating intersection lines, splitting each triangle through which an intersection line passes, sectioning geometries, regrouping facets to form new geometric objects, and mapping each new geometric object to rendering facets. To record modeling process, the method has the steps: allocating a Constructive Hybrid Geometry object, making up each Operating Geometry including a geometry object and operational parameters, adding an Operating Geometry to the object, conducting operations with the facets, and updating operational results. The system is flexible and able to create fine and variant geometric models with primary geometric objects, extended geometric objects and surface patches.