Abstract: It is important to test low noise block downconverter for assuring quality of whole network.The paper introduced design of a control board of automatic testing system for LNB based on LabVIEW.The control board takes 8255 chip as control core and controls position movement of tested LNB and signal switch.And it takes LabVIEW as development platform to program drive of control board and simulates returning end signal of positioning at one time.Trial running result showed that the control board can realize positioning of tested LNB and signal switch and display positioning status of tested LNB real-timely.