As an important technology in the field of computer-aided test,virtual instrument technology is the product of combination of modern computer technology and instrument technology.This paper introduced the design of the virtual spectrum analyzer based on B/S model.This virtual spectrum analyzer is mainly used for analyzing signal with noise which is produced by signal generator.The virtual spectrum analyzer consists of signal generator,digital filter,parameter measurement,frequency spectrum analysis,harmonic analysis and remote network monitor.The experiments showed that the virtual spectrum analyzer can realize functions such as the sampling signal display,analysis,remote network control.The virtual spectrum analyzer works smoothly with satisfactory results and reliable performance.