Wireless sensor networks (WSNs) are gradually used to perform a cooperative monitoring task for critical applications. For conserving energy, powerful nodes are activated only when an interesting event is detected, while low-cost and error-prone sensors dominate the primary quality of surveillance (QoSu) when an event just appears. However, an individual low-cost sensor is unreliable due to environmental interference, battery depletion or the use of low-cost hardware. The K-coverage configuration, which ensures each location is covered by at least K active sensor nodes, is widely used to increase the confidence of detection. The challenge here is how to preserve a desired K-coverage efficiently. In this paper, we proposed energy-efficient and fault-tolerant algorithm to guarantee the K-coverage configuration on WSNs while maximizing the system lifetime.