Abstract: In this paper, a numerical simulation method is used to investigate the development of water-con-ducting fissure zone in overlying strata resulting from the extraction of horizontal or gently dippingmedium thickness orebody under water with back-filling. The results show that the maximum devel-oping height of actual presented zone decreases, and the developing shape of latent zone varies bymeans of being arranged panel barrier when the extracting 8cale develops to a certain extent. The con-clusions will play important role in guiding the mine safe production.