A critical aspect of applications with Wireless Sensor Networks (WSNs) is network lifetime.Power-constrained WSNs are usable as long as they can communicate sense data to a processing node.Poor communication links and hazardous environments make the WSNs unreliable.Existing schemes assume that the state of a sensor covering targets is binary:success (covers the targets) or failure (cannot cover the targets).However,in real WSNs,a sensor covers targets with a certain probability.To improve WSNs’ reliability,we should consider that a sensor covers targets with users’ satisfied probability.To solve this problem,this paper first introduces a failure probability into the target coverage problem to improve and control the system reliability.Furthermore,we model the solution as the α-Reliable Maximum Sensor Covers (α-RMSC) problem and design a heuristic greedy algorithm that efficiently computes the maximal number of α-Reliable sensor covers.To efficiently extend the WSNs lifetime with users’ pre-defined failure probability requirements,only the sensors from the current active sensor cover are responsible for monitoring all targets,while all other sensors are in a low-energy sleep mode.Simulation results validate the performance of this algorithm,in which users can precisely control the system reliability without sacrificing much energy consumption. A critical aspect of applications with Wireless Sensor Networks (WSNs) is network lifetime. Power-constrained WSNs are usable as long as they can communicate sense data to a processing node .Poor communication links and hazardous environments make the WSNs unreliable .Existing schemes assume that the state of a sensing covering targets is binary: success (covers the targets) or failure (can not cover the targets) .owever, in real WSNs, a sensor covers targets with a certain probability. To improve WSNs’ reliability, we should consider that a sensor covers targets with users’ satisfied probability. solve this problem, this paper first introduces a failure probability into the target coverage problem to improve and control the system reliability. Future, we model the solution as the α-Reliable Maximum Sensor Covers ( α-RMSC) problem and design a heuristic greedy algorithm that efficiently computes the maximal number of α-Reliable sensor covers. managed efficiently the WSNs lifetime with use rs’ pre-defined failure probability requirements, only the sensors from the current active sensor cover are are for monitoring all targets, while all other sensors are in a low-energy sleep mode. Simulation results validate the performance of this algorithm, in users can precisely control the system reliability without sacrificing much energy consumption.