After entering into service, in order to maintain and improve the performance of civil aircraft and engine, to rectify the unsafe conditions constantly found in service, to ensure the safety and airworthiness. Airlines or operators must comply with requirements defined in ICA documents via relevant technical works. Through the study of the relevant certification regulations and advisory circulars for ICA documents, it indicates that, except for instructions related to overhaul or heavy maintenance, all ICA documents for civil aircraft and engine should be approved by agency prior to aircraft delivery to airlines or issuance of the airworthiness certification by agency, whichever is late. This paper interprets the related airworthiness requirements for ICA documents of engine, enumerates the list of some type civil engine ICA documents, conducts the research on the content of important ICA documents. It makes a useful exploration on the continued airworthiness system of civil aircraft propulsion system. Throughout the whole life of civil aircraft, ICA documents should be considered as an extension from the design and manufacture phase to the service phase for the civil aircraft and engine. In fact, the ICA documents is a product of technical publication as equally important as the actual aircraft hardware, which is essential to safe and reliable operate the civil aircraft for airlines and operators.