This paper describes an innovative free-form modeling system, Virtual Clay Modeling System (VCMS), in which users can directly manipulate the shape of a virtual object like a clay model in real world. With this system, some disadvantages of interaction with computer aided industry design (CAID) systems can be resolved. In order to enhance the immersion feelings and improve the controlling abilities to cut, paste, and compensate of VCMS, we use Spaceball 5000 and PHANTOM Desktop to assign the set of interaction tasks. During the process of realizing 6 degree-of-freedom (DOF) haptic feedback modeling control, we developed and accomplished the device interfaces with Open Inventor and Qt application framework. VCMS provides us a good immersion of allowing for effective modeling in a virtual world.