Abstract: Oral malodor, also known as halitosis, is a widespread problem, which is mainly caused by volatile sulphur compound（VSC）. VSC is produced by Gram- negative anaerobic bacteria. Oral malodor reduction may be obtained by a combination of chemotherapeutical and mechanical treatments. However, these modalities exhibit only temporary effects. And some undesirable side effects may occur when they are used in the oral cavity for long periods. Streptococcus salivarius is known to be normal flora in the mouth. They might have potential applications as adjuncts for both the prevention and treatment of oral malodour.