Liquid polybutadiene with higher content of 1,2-vinyl group (1,2-polybutadiene) can be produced by the living-anion polymerization method. It is being used as an additive for various lubber products such as EPDM, SBS, HNBR for a long time since 1,2-vinyl units react each other as cross linker and create network formula contributing improvement of hardness, elasticity and oil-resistance in the rubber products. In this study, we carried out the evaluation of the epoxidized 1,2-polybutadinene as an additive for formulation of chlorosulfonated polyethylene rubber. As a result, the excellent acid resistance could be obtained in addition to the improvement of mechanical properties such as tensile strength or elastic module. This result is indicating that the epoxidized 1,2-polybutadiene can be used not only as a modifier for mechanical properties, but also as an acid acceptor of halogenated rubber formulations instead of lead monoxide, which is being regulated more strictly by the amendment of REACH and RoHS.