The containment structure of nuclear reactors is the most crucial barrier to releasing radioactive materials into the environment and protecting the reactor against external hazards such as earthquakes and floods. After the Fukushima nuclear accident, the safety of this structure in the earthquake has received much attention. Iran is also located in a region with high and very high seismic hazards and is essential. In this study, the seismic fragility curve of the containment structure of pressurized water reactors used in Bushehr has been determined by considering different failure modes. For this purpose, a computer model simulated in ABAQUS software and incremental dynamic analysis (IDA) have been used. The finite element model has been validated using a lumped mass model. Different failure modes are defined in terms of critical stresses in concrete, rebar, tendons, and steel plate attached to the containment body. Critical points of containment have been identified in terms of these failures. Concrete materials fail at a lower acceleration than other materials. At peak ground accelerations of less than 0.2 g, concrete remains elastic, and no cracks are formed; however, at peak ground accelerations of 2.2 g to 2.75 g, concrete cracks of more than 2 mm form, which allow the release of radioactive materials into the environment. The parameters of fragility, median acceleration capacity, and logarithmic standard deviation of median acceleration capacity were determined to be 2.251 and 0.155, respectively.