A novel two-step synthesis strategy based on a liquid neodymium phosphate ester (Nd(P 507 ) 3 ) catalyst was used to synthesize diene-styrene di-block copolymers with high cis -1,4 unit content, such as butadiene-styrene (PB- b -PS), isoprene-styrene (PI- b -PS), and so on. The strategy not only makes full use of the high cis -1,4 stereo-selectivity of the rare earth catalyst to conjugated dienes, but also adjusts the electron cloud density of the catalytic active center by introducing triphenyl phosphine (PPh 3 ). Thus, the catalytic activity of the neodymium-based catalyst center toward styrene has been largely improved, and a series of PB/PI- b -PSs with high cis -1,4 unit content (98.3 and 98.1% respectively), narrow molecular weight distribution and controllable block ratio were successfully synthesized. Herein, molecular weight ( M n ), molecular weight distribution ( M w / M n ) and microstructure of the block polymers were characterized using SEC-MALLS, FT-IR, 1 H NMR, 13 C NMR and DSC. The DSC curve of a PB- b -PS with 98.3% cis -1,4 unit and 18.6% polystyrene content shows a T g of -103.1 °C, which means it has relatively excellent mechanical properties at lower temperature. The results show that these PB/PI- b -PS materials have good application prospects in harsh low temperature environments.