Abstract: Because of its well hydrogen isotope effect, its resistance to poisoning by impurity gas and its ability for retaining the ³He created by tritium decay, palladium is widely applied in tritium process, but tritium aging affects its applied properties. It’s important for tritium process to master aging effect on palladium thermodynamics pro-perty, mechanical property and microstructure. By observing the modifications of p-C-T isotherms, we find that aging leads to the decrease of plateau pressure, increase of plateau slopes and tritium heels, and decline of the mechanical properties. The decay product 3He accumulates in palladium and the forming of He bubbles leads to the swelling of lattice. The defects, such as clusters of self-interstitial, dislocations, dislocation loops, can be observed during aging.