Abstract: Based on the data from the gravity and magnetic profiles across the Qiangtang basin, combined with the data of plan gravity and magnetic anomalies, through an analysis of the features of the gravity and magnetic anomalies and by using the method of potential-field transformations and forward-inverse fitting, the authors deduce the burial depth of the basement, fault structure and style of the Qiangtang basin and discuss the petroleum prospects of the basin. They think that the basement of southern Qiangtang has a shallow burial depth and occurs as steps with complex structure, while the basement of northern Qiangtang is deeply buried. The Lungmu Co-Shuanghu Lake structural belt between the northern and southern Qiangtang have conspicuous gravity and magnetic indications.