Abstract: High speed data acquisition and storing is a key technique of the software radio. If the real time signal can be recorded without error, then it can be analyzed with many modern methods of signal processing, which will lead to more accurate results. A high speed data recording scheme based on software is suggested in this paper. To realize it one only needs a DAQ card and a SCSI hard disk. Overleaping the file system is the characteristic of this method, which makes the real time data recording speed up to 40Mb/s. This method has been applied to some devices and works well.