In recent years, Wireless Sensor Networks(WSNs) research has been carried out with the goals of achieving high security and energy efficiency. In a WSN, sensor nodes are vulnerable to physical attacks because they are deployed in an open environment. An attacker can inject a false report into networks using these vulnerabilities. F. Ye et al. proposed statistical en-route filtering to prevent false report injection attacks. In order to effectively use their scheme, techniques for determining thresholds using fuzzy logic have been studied. To effectively apply these techniques to the network, an appropriate update period should be set according to the network environments. In this paper, we propose a security period update method in order to improve the lifetime of the network in the statistical en-route filtering approach based on a wireless sensor network of the cluster environment. The experimental results show that up to an 11.96% improvement of the energy efficiency can be achieved when the security threshold is set to the optimal period.