To investigate the seismic Fragility of a medium-span steel tube concrete arch bridge under pulse-type earthquake excitation, this study establishes a finite element model based on a specific medium-span steel tube concrete arch bridge. Twenty pulse-type and twenty non-pulse-type earthquake ground motion records are selected for conducting Incremental Dynamic Analysis (IDA) on the bridge structure. The arch ribs, upper arch columns, and hangers of the arch bridge are analyzed as vulnerable components, defining five damage states. Fragility curves for components and the bridge system are obtained through lognormal distribution fitting and first-order limit method, respectively. A comparison of the Fragility of the structure under pulse-type and non-pulse-type earthquake excitations is conducted. The results indicate that the exceedance probabilities of various damage states for components and the bridge system under pulse-type earthquake excitation are higher than those under non-pulse-type earthquake excitation.