Regarded as a random signal, Potential Field can be processed by two-dimensional autocorrelation method. In this way, some objective tectonic information can be effectively acquired. The two-dimensional autocorrelation method can overcome some subjective factors of horizontal directional derivatives(0°,45°,90°,135°). In addition, the result from the analytical method is clear and straightforward, and the strikes of some boundary faults can be clearly defined. The shortcoming of the method is that some information of the data window margin may be lost. Nevertheless, this problem can be easily solved, for example, by sliding analytical windows or by adding grid data to windows. The application of this method to northwestern Ordos Basin on the basis of aeromagnetic anomalous data shows that some boundary faults, such as Helanshan fault, Langshan-Bayanwulashan fault, Zuozishan-Hengshanbao fault and Xiaosongshan fault, can be directly detected. It is also found that Helanshan fault is not very deep.