At present, the test and maintenance of weather radar mainly rely on traditional desktop instruments. Its limited functions and poor mobility restrict the diagnoses and repair of radar malfunctions, and induce a baneful influence to meteorological service. The principles and function parameters of radar receivers are analyzed. The hardware framework and software characteristics of the virtual instruments are introduced. Taking the IF band width testing as an example, the design ideas, work principles, and operating methods of the virtual instruments system are discussed. With the advantages of using portable modularized PXI instruments as hardware and software programing as its kernel, having overcome the disadvantages of traditional ones and having good environmental adaptability and capability of function expansion, this system is especially suitable for the site tests in radar stations.