The results of the WAXD analysis of cis polybIutadiene containing brans-1，4 units，synthesized with dual catalyst (vanadium-and cobalt-based) systems，and cis-polybuta-diene containing syndio-1，2 units，synthesized with two cobalt catalyst systems，were presented in this paper．The erystallinity of both cis-polybutadierie was proved to be contributed by the pre-sence of trans-1，4 polybutadiene sequences and syndio-1，2 polybutadiene sequences respe-ctvely in the cis-polybutadiene. The degree of erystallJnity of polymer is increased with the increase of trans-1，4 content in the cis-polybutadiene cont containing trans-1，4 units and with that of syndio-1，2 content in the cis-polybutadiene containing syndio-1，2 units．From

the relationship between the degree of crystallinity of the polymer and trans-1，4 content or syndio-1，2 content，it was shown that the degree of crystallinty of blend of homopolymers was hi-gher than that of copolymers．The blends held the transition feature of crystal modifi-cation and not so for copolymers at 50℃．