Abstract: Based on PFC3D discrete element, an inversion simulation on the Tanggudong landslide dam on Jinsha River in 1967 was carried out, and based on the inversed parameters we predicted the accumulation process of strong deformation zone A of the landslide dam. The following conclusions can be drawn. (1) By inversion analysis, we obtained a set of reasonable mesoscopic mechanical parameters. (2) The strong deformation zone A slid downward 1600m to the river valley, forming a barrier dam. The cross section of barrier dam was ladder shape, which was high at middle and low at both upstream and downstream side, the width of top, width of bottom and height of the dam was 437.9, 994.39, 92.65 m respectively. (3) Under three different inflows, the simulated peak flood of dam break were much larger than the check flood at the proposed dam site of Lenggu hydropower station. For simulation of barrier dam accumulation process and accumulation form, PFC3D has a good applicability in obtaining the three-dimensional shape and height of the dam.