Abstract: With respect to the high-density deployment of wireless sensor networks, a NP-complete problem is to be solved, i.e., how to find out the minimal number of nodes with the target region fully covered simultaneously. A new optimal algorithm for selecting the set of nodes is thus designed on the basis of genetic algorithm. With the full network coverage provided and part of redundant nodes entering into dormancy, an optimal coverage set of nodes is formed. A simulation test was done to evaluate the performance of the algorithm for network coverage, and the result showed that it can achieve an optimal selection of the set of nodes in hundreds at low cost, thus prolonging efficiently the network lifetime.