PCB testing system will have a new design idea, the automatic test system based on USB bus and virtual instrument design idea, give full play to the role of the computer, as far as possible the thought of by the computer instead of the traditional instrument, so as to reduce the volume of the instrument itself, reduces the cost of development, so as to improve the efficiency of development. D/A conversion to obtain test excitation signal applied to the simulation test system, and by the test circuit through the test on the bus to the switch matrix, and connected to the switch matrix controlled by microprocessor, its guide clearance is broken at the same time, the PCB board to be tested is fixed to the needle bed, excitation signal by applying to the corresponding position of printed circuit boards, its response can be measured by the test circuit, analog acquisition, into the core control, after A/D conversion, get the corresponding digital quantity, by the software on the PCB feedback and through PCB machine processing, determine whether the PCB board to be qualified. The online testing technology breaks through the previous method of detecting circuit boards with human eyes. The online testing technology has high efficiency and low leakage rate, realizing the automation of the testing field.The system adopts the idea of combining with virtual instrument to reduce the design of hardware and the cost of the whole system. This system is suitable for the application of small and medium enterprises.It reduces the quantity of unqualified products entering the next process, thus reduces the rework quantity of products, improves the production efficiency, reduces the total cost of manufacturing, and improves the profit of the enterprise. Currently, it is a widely used testing technology, and a high-efficiency, high-speed and high-precision testing method. At present, PCB board is used in the field of automatic test of printed circuit board, including the test of uninstalled components and the test of installed components. The current commonly used test methods include: on-off test, in-circuit test, functional test, edge test, optical test and X-ray test, etc.According to the specific characteristics of PCB board, the online test is to select an appropriate test method to combine one or more processes, learn from each other and make up for each other, and apply it comprehensively.