Abstract: Poly(butadiene-b-dimethylsiloxane) diblock copolymers(PB-PDMS) with defined composition apd molecular weight and molecular weight distribution were synthesized by anionic sequential polymerization. Hydrogenation of polybutadiene block in PB-PDMS with p-toluene-sulfonyl hydrazide as hydrogenation agent yielded poly(ethylene-b-dimethylsiloxae) diblock copolymers(PE-PDMS). ¹H-NMR and IR spectroscopy showed that the hydrogenstion reaction was complete. The DSC results shdwed that both the crystallization behavior of PDMS block and the melting temperature of PE block were effected by the composition of PE-PDMS.