Abstract: North Hulunber League of Inner Mongolia is rich in placer gold deposits, where dozens of small-madium scale deposits have been explored. There exists two stages of granits, i.e., Caledonian stage (442 Ma) and Hercynian stage (383-230 Ma). Based on its characteristics on petrology, lithochemistry, Sr-isotope and rare earth elements, the granitic rocks can be divided into two types of genesis, i.e., anatectic type (Ⅰ) and continental crust transformation type (S).The S-type contain higher abundance of gold, because it metasomatized and remelted basement rock with high gold abundance (slate, schist, etc.) This proves that the S-type provided gold source directly to placer gold deposits in this region. Moreover, the fact that natural gold grains are found in artifical heavy placer minerals from S-type granite also confirms that a part of gold exist in natural form.These suggest that we should pay attention to searching gold deposit in the area where S-type granite is developed.