Abstract: To determine the geologic age of the lunar surface is the foundation of the research on the formation and evolution of the Moon, and of the inversion of the processes of lunar geological events. Lack of lunar rock and soil samples limits the range of geological units that can used for isotopic dating. Therefore, the dating using crater size-frequency distribution (CSFD) is employed to obtain the geologic ages of broader regions on the lunar surface. However, the presence of secondary craters will lead to a deviation in geologic age which is obtained by CSFD method. Thus, to get a more accurate geologic age, secondary craters should be eliminated. This paper presents a method to identify secondary craters based on the distribution of iron element on lunar surface. First, the method assumes that the iron content in secondary craters is close to that in lunar regolith. Then, band ratio method is utilized to acquire the iron content. Finally, secondary craters are distinguished from primary ones in terms of the difference of iron content between craters and lunar regolith. The effectiveness and robustness of the proposed method were tested using MI multispectral data of the Japanese Selene Mission. The experimental results show that the geologic age deviation compared with the known isotopic dated ones is less than 0.04Ga, which shows good consistency. Compared with other secondary craters identification methods, the proposed approach is proven to be more effective and robust.