To modify the fluidity and crystallization properties of poly(butylene succinate) (PBS), glycerol and pentaerythritol were selected as branching agent. A range of PBS polyesters with varying types and amounts of branching agents were synthesized by direct esterification-polycondensation method. FT-IR, 1H-NMR, DSC, GPC, and capillary rheology test were employed to investigate the impact of the type and quantity of branching agent on the structure, molecular weight, thermal properties, rheological properties, and crystallization properties of the materials. The results show that the relative molecular weight of branched PBS is higher than that of linear PBS, but the melting point is almost constant, about 114 ℃. POM results show that the addition of branching agent decreases the crystallinity and grain size of PBS. The results of melt index rate and capillary rheometer show that the intrinsic viscosity of branched PBS is lower than that of linear PBS, while the melt index of branched PBS is higher than linear PBS, and it increases with the increase of branched dose. Compared with linear PBS, the melt strength of branched PBS is increased by 135.3% (0.3% glycerol) and 205.9% (0.2% pentaerythritol), respectively. The results of this study can lay a foundation for the development of branched aliphatic polyester and its application in the field of fiber.