Abstract: The responsiveness and transcatheter embolization with magnetic gelatin micro-spheres(MG- ms)in dog kidney were reported.In experiments with magnet using a constant flowapparatus such as roller pump the percent retention was determined by counting the carrier retainedby the magnetic field and divided by the total starting counts,Factors influencing the percent retentionof MG-ms include :velocity of medium flow ,magnetic field intensity,α- Fe₂O₃ content in theMG-ms,viscositv of the medium and so on。Transcatheter embo1ization with MG-ms(10～ 30 um)was performed under external magnet control in dog kidney.The result of angiogram and histologica1section showed that the MG- ms were in the arteries ,arterioles , and glomerular capillaries with noadverse teactions.The embolized effect with magnet field was more prominent than the group withoutmagnet field.These results show that the MG-ms is a promising embolic agent for treatment of renalcancer under external magnet control。