Abstarct: Geophysical methods are routinely used for the exploration of the subsurface masses. They can provide appropriate information about the position of such masses. Amongst the geophysical methods, gravity and magnetic surveys as the potential field methods, are recognized to be efficient and inexpensive methods which are particularly used in prospecting large areas. The measured data should be interpreted as soon as the field operation has ceased. Determination of shape, position and edges of the subsurface bodies are principal in the interpretation of the potential field data. It has been suggested that the analytic signal method is superior in the determination of the anomalies edges. In this research, a three dimensional analytic signal method was used to determine the edges of the gravity and magnetic data. In order to investigate the capability of the analytic signal method in edge detection, this filter was first applied on the artificial gravity and magnetic anomalies. The results were then compared with those obtained using vertical and horizontal derivatives, horizontal gradient and local phase filters. It was found that, the local phase filters in particular, theta filter which is derived baxsed on the analytic signal and horizontal gradient of the potential filed anomaly, more accurately detected the edges of the artificial mode. All computations were carried out by providing the necessary routines for the multi-purpose MATLAB software. For further evaluation of the method in edge detection, the three dimensional analytic signal method and theta filter were applied on the real gravity and magnetic data measured at Dehno area. These methods could properly detect the edges of the Dehno anticline