Abstract: Two types of floating pellets in stomach were prepared. The first one： floating alginate pellets containing ethylcellulose and clarithromycin (AE)were pellets with dispersed ethylcellulose in the alginate gel matrix. The second one：ethylcellulose microspheres containing clarithromycin (Em) were first prepared by the emulsion solvent diffusion method, and then alginate pellets containing ethylcellulose microspheres (AEm) were prepared. The effects of processing parameters on morphology, size distribution, drug loading, in vitro drug release profiles, in vitro floating property of pellets were investigated. The results showed that about 80% of drug incorporated in AE was released at 2 h, while AEm with moderate drug content had sustained drug release property. The accumulative drug-release percent of AEm in vitro at 6 h were 65.9%—78.8%, and AEm could float in acetate buffer solution for more than 8 h.