Facsimile, as a traditional transmission method of static image file, is an important part of modern communication technology. This paper analyses the status of facsimile over IP (FOIP), compares the Storage- and-Forward and Real-Time implementation standards, then based on embedded SIP voice gateway gives the design and implementation of the pure software T.38 real-time facsimile module. This module is composed of T.30 Soft Modem, processing PCM data, and T.38 protocol stack processing IFP packets. These two parts exchange data through DATAPUMP. This module has weak coupling and high portability, and has been put into practice.