The active electrolocation technology has been developed for near 60 years and played a significant role in the field of biomimetic sensor. But the influence of the edge characteristics of detected objects on underwater active electrolocation system was rarely investigated. In this paper, an experiment system based on the underwater active electrolocation technology is built. The amplitude information-frequency characteristics (AIFC) for different probed objects with the different edge characteristic and approximate volumes are investigated. Two sets of different edge characteristic shapes (cylinder and cuboid, cone and pyramid), whose volumes are little difference in each sets, are carried out in the same materials to deeply study on the effect. The height variation curve (HVC) is employed to compute the frequency inflection point (FIP) of AIFC for the system. According to experiment results, we find that the FIP for the probed metallic objects with similar volumes is weighty associated to the edge characteristics of objects, while the FIP for the plastic has nothing to do with the edge characteristics of objects. It may have reference value for physical mechanism of weakly electrical fish active electrolocation system.