Abstract: Seepage failure of rockfill dam panels seriously threatens the safe operation of large dams. In order to achieve accurate evaluation and detection of micro-seepage defects in panels, taking a specific concrete-faced rockfill dam as an example, on-site tests were conducted on panels above and below water using electrical resistivity tomography and the pseudo-random flow field method. This study analyzes the distribution characteristics and development trends of micro-seepage cracks in the panels, reveals the causes of crack formation, and proposes targeted prevention and control recommendations. The results indicate that: (1) Electrical resistivity tomography, by utilizing different electrode deployment schemes, can relatively accurately identify the location and extent of cracks in panels above water, while the pseudo-random flow field method, based on abnormal current values, can roughly pinpoint high-risk seepage areas in panels below water. (2) Cracks in the concrete panel are mostly situated near the vertical joints in the central part of the dam, and their morphology is predominantly vertical strip-shaped with a certain width. However, the development depth of these cracks remains relatively shallow, and they have not formed penetrating seepage channels causing damage. (3) The formation of panel cracks is primarily attributed to the combined effects of material deterioration, structural stress, and hydraulic action, presenting as a progressive damage process. Taking targeted prevention and control measures at different development stages of the cracks can offer valuable reference suggestions for their effective full life-cycle management.