The I/O performance test system of inverter is designed. ADlink PCI board and signal regulating panel are core of hardware platform. The software uses the mixed programs, that is, the graph control of Labview and Microsoft Visual C++. Based on the eight analog inputs, two analog outputs, three digital inputs and four digital outputs provided with specific application, we fulfill the following assignments: the dynamic monitoring of three-phase input current/voltage, DC-bus voltage and actual rotation speed, curve drawing and data storage. The computer could give the enable signal and analog speed of inverter, besides the failures are read and displayed. Finally the harmonic analysis and the balance analysis of three-phase current/voltage are realized.