Abstract: As a drug for lymphosarcoma,pingyangmycin(A5)is not widely used because of its toxicities ,short half-life and low affinity to lymph.For the purpose of delivering A5 to the lymph system to strengthen and sustain its effects and to lower its toxicities ,its gelatin microspheres-in-oil emulsion(S/O)was studied　in vitro and in vivo.By ultrasonication ,gelatin microspheres with diameters of 1.67±0.69 μm were homogeneously dispersed in oil to form the S/O,which was a pseudoplastic flow and stable under 0℃ for at least 1 month.With the content of 14.03±0.15 mg· ml^-1, A5released from the emulsion in a zero order rate with t_0.5 of 12.0h.In vivo experiments showed that the S/O emulsion exhibited potent lymphotropicity ,prolonged plasma concentration and a probably lower pulmonary toxicity.