A local and formal RC frame building in Wenchuan dicstrict, named Shuang-he market building which is damaged in 2008 Wenchuan earthquake, is studied by nonlinear finite element method. By using probabilistic seismic demand model (PSDM), the seismic fragility assessment of the RC frame is demonstrated on RC frames. Probabilistic seismic demand model (PSDM) for RC frame structures was built to assess the safety levels of the actual RC frames representative of design and construction practices in the Wenchuan county town. The fragility curves for immediate occupancy, significant damage, and collapse prevention damage levels of the RC frame building are analyzed. The result reveals the safety levels of RC frame building in Wenchuan district before the 2008 Wenchuan earthquake.