Abstract: The seepage failure of piping is one of the main reasons contributing to the break of earth-rock dam. It is of great significance to study the change of seepage field in the piping process of earth-rock dam by model experiment. By using the method of simulating piping leakage with preset piping passage, a piping break-out model of scale indoor homogeneous earth dam is established, and the seepage field data of the earth dam model are obtained by arranging a small-range percolator, the variation of seepage field in the whole process of earth dam model from impoundment to seepage failure to break is deeply analyzed and studied. It is found that,during the storage stage, the seepage pressure at the same axial distance is lower than that at the non-piping section, but the peak time is earlier than that at the non-piping section. During the burst stage（open flow and breach formation stage）, the seepage pressure in the dam body drops suddenly, and the closer to the piping section, the earlier the time and the larger the magnitude of the pressure drop. This knowledge can be used for reference in the prediction and early warning of piping failure of earth-rock dams.