Abstract: Taking a rotary actuator in an aircraft transmission system as an example, the impact of the “breathing effect” on the reliability of the aircraft transmission system was verified through environmental tests. Based on mixed operating conditions such as water vapor, corrosion, and low temperature, the corresponding test phenomena of the rotary actuator were obtained. The results indicate that under different temperature, humidity, and pressure changes, water vapor is prone to enter the interior of unsealed products, resulting in a “breathing effect”. Especially in marine flight environments, corrosive elements contained in water vapor can accelerate the corrosion of metal components inside the product, leading to internal product corrosion and the occurrence of jamming. Through experimental verification and fault mechanism analysis, the causes of respiratory action were verified and improvement suggestions were proposed to improve the reliability of product design.