It is an inevitable trend that the fax function is integrated into the traditional IP voice gateway. This paper analyzes the IP fax technology and development situation and proposes a project that adds a software fax module to the gateway without any change of the hardware, so that the gateway can be able to store and forward faxes. The paper gives the fax module’s design and implementation based on Blackfin+uClinux platform. After testing, the voice gateway can successfully send and receive faxes.