Abstract: Electroless ¹⁰³Pd plating and electroless Ag plating and chemical ¹²⁵I depositing were took place on the surface of carbon rods in turn, which was a reliable method for the preparation of ¹⁰³Pd-¹²⁵I hybrid brachytherapy seed cores. ¹⁰³Pd and ¹²⁵I were deposited on the same substrate effectively through silver coating as a bridge. The process of electroless Ag plating was a novel and important step in the preparation of ¹⁰³Pd-¹²⁵I hybrid seed. In this work, the process of electroless Ag plating was studied using 0.5×3.0 mm carbon rods with palladium coating as substrate, silver-ammino complex as precursor, ^110mAg as radioactive tracer, and hydrazine as reductant. The optimum conditions were AgNO₃ 2g/L，Na₂EDTA 40 g/L，NH₃•H₂O 16.25%，H₄N₂•H₂O 5‰，pH=10，t=60 min，and T=35 ℃. Sliver deposited on each carbon rod was uniform, and sliver-coating was white and smooth.