A new kind of virtual sweep signal source which can be used to output specific sweep signal according to(users') configuration and can be widely applied to frequency characteristics measurement in the field of mechanics,electrics and electronics,is developed by using Dot Net software engineering technique,C/S architecture and general data acquisition platform.The virtual instruments not only make up the intrinsic defect of traditional instruments based on hardware components in high performance,remote control and data processing,but also indicate the powerful life and nice future of virtual instrument technologies.