Connected dominating set is widely used to construct a virtual backbone for effective routing in wireless sensor networks. The k-connected dominating set, where at least k disjoint paths between any pair of nodes exist, is used to meet the fault tolerance requirement of wireless sensor networks. It is an open problem of finding a minimum approximation ratio, measured by the ratio between the number of nodes in the constructed virtual backbone and the number of nodes in the optimal minimum connected dominating set. In this paper, we propose Crossed Cube Ring Algorithm (CCRA) to make the k-connected dominating set virtual backbone with a lower approximation ratio than any existing algorithms. Both theoretical analysis and simulation experiments demonstrate that CCRA can reduce the approximation ratio by 20% than any other algorithms. Therefore, CCRA can be used to construct more compact k-connected dominating set than the conventional algorithms.