In this paper, the reflow soldering process without flux for Ge window of infrared detectors is investigated, and soldering tests on Ge windows and Kovar alloys with different plating systems are conducted using In solder pieces in a reducing atmosphere. Through the analysis of weldappearance, vacuum leak rate, X-ray NDT, and reliability test of window components soldered under different plating systems, it is shown that gold plating on the soldering surface of Ge windows and Kovar alloys can be used to prepare window components that meet the requirements of sealing and environmental adaptability under reflow soldering in a reducing atmosphere.