Time perception is a fundamental ability of human beings．Daily experience indicates that time perception is easy to be affected by emotion. However, the emotional influence was often accompanied by active attention and explicit motor response in previous studies. Here the question whether implicit time perception could be influenced by emotional faces is addressed. Observers actively completed a visual discrimination task of emotional faces (fearful, happy and neutral faces) while they passively listened to a sequence of tones with 80% standard stimulus onset asynchronies (SOAs) (800 ms) and 20% deviant SOAs (400, 600, 1 000 and 1 200 ms). Event-related potentials (ERPs) were recorded for frequent standard SOAs and rare deviant SOAs. The two short deviant SOAs (400 and 600 ms) elicited two changed-related ERP components: the mismatch negativity (MMN) and the P3a. The MMN amplitude, which indexes the early detection of irregular time changes, was modulated by facial emotion. Fearful faces elicited reduced MMN as compared with happy faces and neutral faces did for the shorter deviant conditions, and happy faces elicited enhanced P3as as compared with fearful and neutral faces did. The current ERP study suggested that shorter time perception of auditory modality was affected by visual emotional faces, and fearful faces decreased the accuracy of implicit time perception.