The invention discloses polymeric carbodiimide compounds and a preparation method thereof. In the invention, a diamine containing an epoxy group is subjected to a substitution reaction to form a diisocyanate, polycondensation is performed, purification is performed, and therefore one polymeric carbodiimide compound (I) shown in the description is synthesized. According to the polymeric carbodiimide compounds provided by the invention, the epoxy group is introduced into the compound molecular structure, so that the rigidity of a polymer molecular chain is greatly improved, the thermal degradation temperature of the carbodiimide compounds is improved, the defect that monocarbodiimide is easy to transfer from compounds such as polyesters and polyurethanes at high temperatures is overcome, andthe hydrolysis resistance of the material is improved; the compounds can be used as a hydrolysis-resistant stabilizer to be used for thermoplastic polyurethanes, polyurethane elastomers, polyurethaneadhesives and polyester elastomers, and can be used particularly in the photovoltaic industry, biodegradable materials and the like; and the synthesized polymeric carbodiimides with different polymerization degrees have no smell and a low yellowing index, and can be widely used in fields with higher color requirements.