As the mobile communication technology develops rapidly, traditional communication devices based on proprietary hardware have limited function and are hard to upgrade, which cause a compatibility issue for a variety of communication protocols and software versions. Software defined radio technology has the advantage of flexibility and openness, and can solve these problems easily. We present a multi-rate digital intermediate frequency (IF) system implemented by FPGA. The system is designed in a full duplex mode and supports multi-rate transceiver; it can also be configured according to specific applications in order to achieve a variety of data conversion rates. The system includes a mixer module, a sample rate conversion (interpolation and decimation) module, and a low-pass filter module. It realizes 32, 96, 480 times down/up sampling and 240kHz down conversion process. The spurious signals are effectively suppressed while the signal stopband attenuation can reach 60dB. With flexible system configuration, the module is optimized and reused, which can save hardware cost and improve the performance.