Abstract: The rapamycin-loaded spherical microparticle based on biodegradable linear-dendritic diblock copolymer is prepared by dialysis method.Scanning electronic microscope(SEM),dynamic light scattering(DLS) and UV spectrophotometer were used to investigate morphology,size and in vitro release behavior of these particles.The results showed that the drug content and encapsulation efficiency of drug-loaded microparticles prepared by diblock copolymer,as well as those prepared by dumbbell-shaped triblock copolymer,could be more than 40% and 90%,respectively.Meanwhile,the mean size of those microparticles reduced significantly and it showed an obvious sustained release as well.