3DStudio（3DS） is a file structure of 3dsMax used to store model information, which is one of the industry's standard format in 3D software. In order to ensure the models of different system can be called freely, to solve the problem that the different model format is not compatible in visual system, and to reduce the storage space of 3DS file, this paper proposes to use the Backus-Naur Form (BNF) specification to describe the 3DS file. This paper describes the characteristics of the BNF and the method of describing and analyzing the 3DS file structure, and takes the 3DS file of Tethys model as an example, using BNF to formally definite it, thus forms a unified format of standardization management, which facilitates retrieval and application of search engine.