Abstract: In order to meet the stringent requirements of the new energy industry for extreme bending performance of hot-dip galvanized complex phase steel, two 780 MPa grade hot-dip galvanized complex phase steels （Steel 1 and Steel 2） with different composition systems and microstructures were developed through tailored alloy design and process control. The phase morphology, distribution, grain size, and elemental segregation behavior of both steels were systematically characterized using scanning electron microscopy（SEM）, electron backscatter diffraction（EBSD）, electron probe microanalysis（EPMA）, as well as tensile and bending tests, and their mechanical and bending properties were compared. The results indicate that both steels comprise bainite, tempered martensite, and ferrite, yet exhibit distinct microstructural characteristics.Steel 1 features martensite islands with an average size of 2.1 μm and ferrite grains averaging 2.5 μm. Its microstructure consists of 48%（volume fraction） ferrite and only 16% bainite, contributing to a lower yield ratio and higher elongation. However, significant segregation of carbon and manganese is observed in Steel 1, with local mass fractions reaching up to 1.46% C and 4.5% Mn. This localized chemical heterogeneity induces strain localization and damage accumulation, leading to the formation of micro-cracks along martensite/ferrite interfaces during extreme bending of steel, accompanied by extensive void nucleation and coalescence. In contrast, under the same annealing conditions, Steel 2 exhibits significantly improved microstructural homogeneity. The average size of martensite islands is refined to 1.8 μm, the ferrite grain size is reduced to 2.1 μm, and the bainite volume fraction increases to 38.4%. Moreover, carbon and manganese are distributed more uniformly in Steel 2, resulting in a higher yield ratio and tensile strength. Although Steel 2 shows relatively lower elongation, no macroscopic cracks are observed under identical bending conditions. This study elucidates the influence mechanism of multiphase microstructure refinement on the bending performance of complex phase steels, providing a theoretical foundation and a technical pathway for developing ultra-thick hot-dip galvanized complex phase steels with superior bending performance.