A Pb‐alloy film preparation technique is proposed and applied to high‐reliability Josephson junctions with small threshold current spreads. Fine‐grained films with the average grain sizes as small as 30 nm are obtained. This is accomplished by condensing Pb, In, and Au molecular beams onto liquid‐nitrogen‐cooled substrates. Fine grains result from AuIn2particles being dispersed finely and uniformly in alloy films. Josephson junctions are fabricated using these fine‐grained films as base electrodes. The threshold current standard deviation is reduced to 2.4%. This is due to the fine grain size and surface passivation treatment for the base electrodes. The cumulative failure is found to be less than 0.13% after 8400 thermal cycles between 4.2 K and room temperature. This is the best value reported thus far. This technique achieves fine‐grained metal alloy films providing new properties. These properties promise to aid development of high‐performance Josephson IC’s.