Abstract: X-ray is produced by SJ-A X-ray tube in China Academy of Measurement and Test Technology, Chengdu,and 80C196KC20 microprocessor is irradiated by X-ray in different directions. The direction is defined along the line which is perpenticular to the surface of the microprocessor. The results of the test show that the effect of X-ray to the microprocessor decreases while the angle changes from 0° to 90°. The main reason is that X-ray may go through different thickness of the crust of device when the device is irradiated in different directions.