With the introduction of new VR/AR devices, realistic and fast interaction within virtual environments becomes more and more appealing. However, the challenge is to make interactions with virtual objects accurately reflect interactions with physical objects in realtime. In this paper, we present a virtual grasping system for multi-fingered hands when manipulating complex objects. Humanlike grasping postures and realistic grasping motions guarantee a physically plausible appearance for hand grasping. Our system does not require any pre-captured motion data. Our system is fast enough to allow realtime interaction during virtual grasping for complex objects.