Abstract: The Kaladawan iron deposit was discovered in the Arkin area in recent years. It is a superlarge iron deposit with controlled reserves of nearly 100 million tons, and characterized by high grade, low sulfur and low phosphorus. Due to the particularity of the surrounding rocks of the deposit, there has been a big controversy on the genesis of the deposit. In this paper, the Re-Os isotopic dating method was used to determine the metallogenic epoch of the five molybdenite samples from the Kaladawan orebody, and the molybdenite Re-Os isotopic model age is 490±11Ma, isochron age is 481.9±7.6Ma. Both are basically consistent within the error range. The ages coincide with the SHRIMP U-Pb ages of the mineralization-related rock of 488±5Ma and 479±4Ma, and there is also diorite exposed near the orebody, which shows close relationship between petrogenesis and mineralization. Combined with petrology, mineralogy and chronological characteristics, the authors hold that the Kaladawan iron deposit is a skarn deposit.