Abstract: There are many mineral resources in the north margin of Altay-Junggar, such as iron, copper, nickel, gold, etc. However, there are some disputes around Junggar about tectonic units and faults division affecting prospecting direction. To further deepen the study of regional mineralization regularity, the newest and largest scale gravity and magnetic information were collected; with the guidance of geophysical gravity and magnetic theory, the authors analyzed characteristics of the gravity and magnetic field by GIS technology, and interpreted the faults in the north margin of Altay-Junggar and the west margin of Junggar. Results show that the two faults were completely different in terms of properties, and there is nothing comparable between east and west Junggar. The fault in the north Junggar is mainly NWW-trending. It is concluded that the Junggar continental boundary should be to the west of Tacheng-Hebukesai. Similar to west Junggar and Calamaili, it is just a local uplift in the Junggar block.