Leakage is one of big security risks in the explosive gas atmosphere. In view of the weak current and detection difficulty of leakage signal, a novel method of leakage detection is proposed. According to leakage transient characteristics, this method takes zero-sequence voltage as the fault threshold value triggering measurement device. Auto-correlation function is used to analyze leakage signal energy and cross-correlation function is used to calculated leakage signal phase relationship in order to identify leakage line further. Theoretical analysis and simulation show that the proposed method can greatly improve the sensitivity of weak leakage signal detection.