NOVELTY - Preparing palladium (103Pd) sealed seed core using palladium (103Pd) as source core material, comprises (i) dipping silver bar in palladium chloride solution, and taking out, washing by using water, and then dipping the bar in alkaline ammonia solution of hydrazine, taking it out and washing by using water, and (ii) introducing the bar in mixing solution (composed of palladium chloride, ethylenediaminetetraacetic acid, ammonium hydroxide and hydrazine), stirring to react under condition of heating in water bath to make layer of palladium (103Pd) cover on surface of the silver bar.    USE - The palladium (103Pd) sealed seed core is useful in medical treatment.    ADVANTAGE - The method: has low production cost: and is environment friendly. The palladium (103Pd) sealed seed core is equally and compactly distributed on the surface of the silver bar, and has wide application range.    DETAILED DESCRIPTION - Preparing palladium (103Pd) sealed seed core using palladium (103Pd) as source core material, comprises (i) dipping a silver bar in palladium chloride solution, and taking the silver bar out, washing by using water, and then dipping the sliver bar in the alkaline ammonia solution of hydrazine, taking it out and washing by using water, and (ii) introducing the sliver bar in a mixing solution which is composed of palladium chloride, ethylenediaminetetraacetic acid, ammonium hydroxide and hydrazine, stirring to react under the condition of heating in a water bath to make a layer of palladium (103Pd) cover on the surface of the silver bar, where the concentration of palladium chloride in the step (i) is 1-10 mmol/l; the soaking time of the sliver in the palladium chloride solution is 1-5 minutes; the concentration of hydrazine is 1-5 mmol/l; the concentration of the palladium chloride in the step (ii) is 3-30 mmol/l; the concentration of ethylenediaminetetraacetic acid is 0.1-0.3 mol/l; the concentration of ammonium hydroxide is 2.5-10 mol/l; the concentration of hydrazine is 5-25 mmol/l; pH is adjusted to 8-12; the reaction temperature is 40-70 degrees C; the reaction time is 30-90 minutes.