Secondary earth faults occur frequently in power distribution networks under harsh weather conditions. Owing to its characteristics, a secondary earth fault is typically hidden within the transient of the first fault. Therefore, most researchers tend to focus on a feeder with single fault while disregarding secondary faults. This paper presents a fault feeder identification method that considers secondary earth faults in a non-effectively grounded distribution network. First, the wavelet singular entropy method is used to detect a secondary fault event. This method can identify the moment at which a secondary fault occurs. The zero-sequence current data can be categorized into two fault stages. The first and second fault stages correspond to the first and secondary faults, respectively. Subsequently, a similarity matrix containing the time-frequency transient information of the zero-sequence current at the two fault stages is defined to identify the fault feeders. Finally, to confirm the effectiveness and reliability of the proposed method, we conduct simulation experiments and an adaptability analysis based on an electromagnetic transient program.