An anti-eavesdropping communication system and method are adapted to be applied in a mobile phone. The mobile phone defines a normal call mode and an anti-eavesdropping call mode. When a user of the mobile phone has a phone conversation using an earphone in the anti-eavesdropping call mode, the system plays a preset audio file which is a recording of the voice of the user saying unimportant things. From the position of a bystander, the recording of the voice of the user interferes with the clarity of what the user is actually saying, and prevents people beside the user overhearing or eavesdropping on the actual conversation which is taking place.