According to EMC Standard,fulfilling one Test-Item generally includes below process: select and configure the parameters of instrument,form and execute the Test-Flow, therefore the main task of EMC is to configure instrument and form the Test-Item. In this paper the authors present a new method using configuration file to describe EMC Test-Item to improve the expansibility and maintainability of EMC test software. Multi-layered software architecture is designed according to EMC test operating sequence, and COM component technology is used to design the core module of each layer to guarantee plug&play for the new program-controlled instruments. Because of using the form of configuration file to describe Test-Item, the new Test-Item will be produced through Test-Engine calling Test-Item Configuration Generator. The Virtual Instrument Software Architecture is used to design and realize the frame of EMC software, and the Visual C++ software platform is used to realize the above design method. Application using configuration file make EMC software has the features of easy to use, easy update and expandability.