Abstract: Ceramic composite armor is a kind of non-standard material. In the process of X-ray digital radiography , the determination of its exposure conditions lacks of corresponding basis. The X-ray digital radiography of SiC ceramic composite armor step test block and 6063 aluminum alloy step test block was carried out by using the equivalent coefficient method under the same tube voltage. The results show that the equivalent coefficient of SiC ceramic composite armor and 6063 aluminum alloy is 0.78-0.89 when the tube voltage is 45 kV-70 kV. The test results have a certain guiding significance for the determination of the X-ray digital radiography technical conditions of SiC ceramic composite armor.