For improving the interchangeability of automatic test system (ATS), a signal-oriented instrument driver is designed based on IVI driving mode. In this paper, after analyzed the software framework of ATS, the signal-oriented instrument driver based on interchangeable virtual instrument (IVI) driving mode is established, then the structure and interface of the driver is studied and the signal-oriented instrument driver is designed by component object model (COM) technique. Experiment result demonstrates that the design can realize the signal-oriented use for instrument driver and improve the interchangeability of ATS.