Abstract: Scheduling nodes to work alternately can prolong network lifetime effectively. Existing solutions usually depend on geographic information which may introduce extra costs and compromise the overall effectiveness. Other node density control algorithms without geographic information do not guarantee a certain effected coverage degree. Analysis on pure stochastic-sleep scheduling mechanism reveals that a certain coverage degree can be met when numbers of nodes are at a certain level. However, the mechanism does not consider network connectivity and therefore its applicability is limited. A new definition of effected coverage is proposed to describe the network coverage maintaining network connectivity at the same time. And based on the definition of effected coverage, a new fractional coverage algorithm is proposed. The algorithm proposed in this paper takes network connectivity into account while maintaining a certain degree of effective coverage. Simulation shows that the proposed algorithm is superior to some existing algorithms in effectiveness, especially in effected coverage. EasiFCCT is designed on the basis of stochastic-sleep scheduling mechanism; so the random property of the proposed algorithm enables an easy implementation. This work is on the assumption that the network system is synchronized, which can be met by using some other algorithm. And the application of this algorithm in asynchronized system remains to be studied in the future.