Abstract: Small space debris may come from both man made space objects and natural meteoroids. The speed of debris is very high and the amount of them is great. They frequently bump on the outer surface of spacecraft, including the porthole, causing especially great damage to the space shuttle porthole, and they pose a potential threat to the porthole glass of space stations flying on a permanent orbit. This paper discusses damage features of portholes of space shuttles and space stations by space debris, and the improvement made by NASA in the porthole design, which may serve as a reference for the porthole structure design of long life and high reliability spacecraft in China.