Abstract: In order to study the effect of heat treatment in air on the hydrogen permeation in/through Pd membrane, Pd membrane was deposited via the electroless plating method and the hydrogen permeation flux of Pd membrane before and after heat treatment in air at 573 K was measured. The membranes were characterized by XRD, SEM, AFM and hydrogen permeation tests. The results show that Pd membrane is compact and defect-free and has a thickness of 5 μm. The hydrogen permeability of Pd membrane at 673 K, 723 K and 773 K are 3.62×10^-9, 5.12×10^-9 mol/(m·s·Pa^0.5) and 6.80×10^-9 mol/(m·s·Pa^0.5), respectively. The membrane treated in air at 573 K has higher surface roughness, larger surface area and more dissociation adsorption sites than the as-deposited membrane, thus improving the hydrogen permeability of the Pd membrane. After heat treatment, the hydrogen permeability of Pd membrane at 673, 723 K and 773 K are 5.32×10^-9, 6.44×10^-9 mol/(m·s·Pa^0.5) and 7.31×10^-9 mol/(m·s·Pa^0.5), respectively. The hydrogen permeability of such Pd membrane is 1.1-1.5 times higher than that of the as-deposited one.