Abstract: The poly(butylene succinate)/magnesium hydroxide (PBS/Mg(OH)2) biodegradable retardant composites were prepared by melt extrusion, and the melting flow index, thermal stability, flame retardant properties, crystallization and melting properties and mechanical properties were studied. The results indicated that MFR of PBS/Mg(OH)2 composites was decreased with the increase of Mg(OH)2. Mg(OH)2 retarded the decomposition of PBS during combustion, and improved the limited oxygen index values of the composites and exhibited excellent anti-dripping properties. Mg(OH)2 increased the crystallization temperature and influenced the melting behavior of PBS due to its heterogeneous nucleation for PBS. When the contents of Mg(OH)2 were less than 40%, the addition of Mg(OH)2 improved the tensile strength, Youngs modulus, blend strength and blend modulus of PBS, but reduced the elongation at break and impact strength of PBS. However, when the contents of Mg(OH)2 were more than 50%, PBS/Mg(OH)2 composites displayed brittle fracture during tensile and blend process due to the poor interfacial interaction between PBS and Mg(OH)2, leading to lower tensile strength and blend strength.