Abstract：Passive ultra-low electromagnetic (ULEM) detection technique is one of the effective means for detection of subsurface and deep geological bodies and resources. However, the curves of ULEM detection obtained using the existing processing methods is sensitive to the noises, which could hamper the correct interpretation of resulting detection signal curves. In this paper, the signal energy was introduced to the processing of the detection signal. Firstly, according to the calculating principle of the signal energy, the energy value of the ultra-low electromagnetic signal for each sampling depth was calculated, and the energy curve was then generated. The obtained energy curve was analyzed and compared with the existing detection curves, such as the maximum and minimum of the magnitude, for some specific applications. The experimental results showed that compared with existing methods, the proposed signal energy method can more accurately reflect the characteristics of the rocks. The proposed method could facilitate the geological interpretation of the resulting curves.