Abstract: Herein, we experimentally addressed the cleaning of spacecraft power-supply module comprising thick film hybrid integrated circuits (HIC) and electrical components assembled in multi-chip module (MCM) technology with the lab-built vapor steam cleaner.The influence of the experimental conditions, such as the treating time/temperature, in the five procedures, including the soaking in liquid cleaning agent, vapor bathing, spraying, rinsing and drying, on the cleanliness and properties of the components was investigated for cleaning conditions optimization.The test results show that the newly-developed vapor cleaning technique satisfies all the stringent requirements and outperforms the conventional cleaning methods, such as manual cleaning, ultrasonic cleaning and water cleanings, because of greater preservation of all mechanical and electrical properties, less damages/contaminations, better cleanliness, higher reliability and longer service life of power supply module in space environment.