Abstract: For aerospace product design and production, three-dimensional digital model has gradually become the main data source of design. In order to solve the problem of digital model becoming invalid over time, this paper proposes a long-term archiving method based on neutral format conversion technology. Firstly, the digital description mechanism of 3D design information of aerospace product is studied, and a unified description method and specification of product data are established. Then, with reference to and by analysis and expanding of STEP standard system, a standard system for product data integration, interaction and long-term archiving is developed; finally, a long-term archiving system is implemented and the validity of long-term archiving of aerospace product data is verified by experiments.