Intermittent faults diagnosis of discrete event systems(DES) can detect intermittent faults in the system in time, but the system may execute unsafe operation during the fault detection. An approach for safe diagnosability is proposed for intermittent faults of DESs. Firstly, the system with intermittent faults is modeled, and the notion of safe diagnosability for intermittents faults of DESs is formalized. Then we construct the recognizer of illegal language to identify the sequences of the forbidden operations. Based on the recognizer, the safe verifier is constructed. In particular, a necessary and sufficient condition of safe diagnosability for intermittent faults of DESs is proposed and a safe diagnosis of intermittent faults is achieved. It is guaranteed that not only each intermittent fault occurring in safe diagnosable DESs can be detected in time, but also the system does not execute any unsafe operation during the fault detection.