As the mobile communication systems develop from 2G to 3G, people require a uniform-spectrum, uniform-architecture. Software radio provides a key solution to the interconnection of various communication architectures and radio standards with different spectrum, poor cooperation capability and so on. Sample rate conversion based software radio is a key technology to implement the interconnection. According to different requirements for the bandwidths and rates of various standards in 3G mobile communication systems, we designed the corresponding sample rate conversion schemes for CDMA2000, TD-SCDMA and compared the sample rate conversion schemes for five standards in 3G with each other. Experimental results show that our designs can effectively reduce the computing cost and memory cost in filtering.