Abstract: Commercial off-the-shelf (COTS) processor needs to be verified by ground-based single event effects (SEE) test before being used in the main controller of the space-borne computers. Compared with the space-level processors of the same price, COTS processors have the characteristics of high integration, complex functions, and rich interfaces. Therefore, it is necessary to customize the design of a SEE test system for it. In this paper, based on the characteristics that the number of COTS processor’s on-chip memory and register are ten thousand times more than that of the space-level processor and that the interface functions of COTS processor are more abundant, single event latchup (SEL) test, memory flip test, register flip test, typical instruction set test, and interface function test were selected as the test items. A set of SEE test system was proposed to effectively test and monitor the power supply current, memory, register, and external interface function of the tested processor.