Generally, mechanical parts in Virtual Assembly systems are donated by rigid bodies. In this paper, we introduce a deformation technique called Lattice Shape Matching algorithm to animate deformable objects in virtual environment. Plenty of experiments have indicated the deformation algorithm can perform well on real-time operation, simulation authenticity and interactive stability. By changing the lattice width value we can animate many objects with different stiffness. With the deformation algorithm, the Virtual Assembly system can be used to the assembly/disassembly of aircraft/vehicle engine, bicycle repair and many other mechanical structure applications.