To investigate the impact of different extreme rainfall distribution patterns on watershed flood characteristics, this study focuses on the Bahe River Basin in Xi'an, Shaanxi Province. A two-dimensional hydro-hydrodynamic model based on the Godunov finite volume method was used to simulate the flood evolution process under six different rainfall intensity scenarios in the upper, middle, and lower reaches (C1:30a-100a-10a, C2:100a-10a-30a, C3:10a-30a-100a, C4:100a-30a-10a, C5:10a-100a-30a, C6:30a-100a-10a). The peak flow and flood inundation risk at two typical cross-sections were analyzed. The results indicate that: (1) The constructed two-dimensional hydro-hydrodynamic model for the Bahe River Basin performed well and can be used for studying flood evolution in the basin. (2) The upstream rainfall intensity has the most significant impact on peak flow, followed by the middle reach, with the downstream having a relatively smaller impact. Among the six extreme rainfall distribution patterns, the C4 pattern has the greatest impact on peak flow, while the C3 pattern has the least impact. (3) Different extreme rainfall distribution patterns have varying impacts on flood inundation areas. When the inundation depth is [0.05, 0.3)m, the C3 pattern has the greatest impact on the flood inundation area, while the C4 pattern has the least impact. When the inundation depth is [1, 7]m, the C4 pattern has the greatest impact on the flood inundation area, while the C3 pattern has the least impact.