Abstract: Under complex natural condition and as the effect of various inner and outside forces for a long time, earth-rock dam is changing momentarily and safety trouble may generate without obvious pre-warning. Especially, because of careless design, poor-quality construction and unsuitable management, many problems may be encountered for the safety of earth-rock dams built earlier. Combined with geological exploration data and two-dimensional finite element calculation of the dam stability before and after reinforcement, this paper analyzed the current anti-slide stability of Longwangyan dam and presented reinforcement measures, for reference for similar dam.