In this paper we propose a maximal independent set (MIS) based giant component formation strategy in random unit-disk graph. This research is motivated by the problem of virtual backbone construction in wireless ad hoc and sensor networks, where the coverage area of nodes are disks with identical radii. The evaluation results show that the MIS-based giant component has the ability to connect most nodes in the MIS and serve as a backbone in the network. Besides, our algorithm is localized and may play an important rule in efficiently constructing a virtual backbone for ad hoc and sensor networks.