Abstract: A slow-releasing antibiotic pill was manufactured,in which polylactice acid(PLA) and starch(20 ∶1, m/m) were used as substrate and florfenicol,a broad spectrum antibiotic in fishery,was used as a model of drug.The physical properties,drug release characteristics and biodegradability of the pills were tested using scanning electron microscopy(SEM),infrared spectroscopy,ultraviolet spectrometer,etc.The results showed that the drug carrier displayed a porous internal structure with good pore connectivity and high porosity(72.5%±1.2%),which is beneficial for florfenicol to be distributed evenly inside the whole pill.The drug demonstrated slowly releasing property due to the degradation of substrates’ i.e.(0.28±0.02) or (0.42±0.03) mg/L after pills floated on or immersed in sea water for 96 h.The experiments about drug-residue,toxicity of PLA and drug releasing pattern were performed in Xiangshan fishery,Ningbo,Zhejiang Province,using pseudosciaena crocea with weight of ~500 g as testing fish In vivo .The result showed that the pills prepared from our present protocol were suitable to be used in fishery cage culture with no obvious toxicity and controlled- releasing.