In VISC the volume models may consiste of a large number of tetrahedrons. It is often required to reduce the number of tetrahedrons for approximating such objects. In this paper we present a new algorithm to reduce the number of tetrahedrons in a tetrahedron-based volume model. The key advantages of the new algorithm are: (1) it is simple to implement; (2) high reduction rates and excellent results can be achieved; (3) It allows a user defined simplification rate to generate a multi-resolution representation. This algorithm has been used in different application areas such as volume rendering, finite elements computation.