The virtual F/A sweep instrument appears as a new instrument when the F/A weep technology using widely but the traditional hardware-oriented F/A sweep instrument couldn't meet the demand. The instrument not only overcomes the shortcomings of the traditional hardware instrument, but also have the advantages of powerful functions, small solidity and easy operation, which make test accurately, fast and simply. This paper introduces the principle, features and operating method of F/A sweep instrument. The designing idea and realizing methods of the virtual F/A sweep instrument are discussed in detail from 3 ways, which include hardware, software and panel. Two applied examples of virtual F/A sweep instrument are given. The virtual F/A sweep instrument has already been used in actual applications.