Model coding is crucial for the integration and effective transmission of digital highway information models at various stages throughout their lifecycle, enabling integrated model management and analytical applications. By studying the construction methods of domestic and foreign highway engineering information model identifiers and analyzing the advantages, disadvantages, and current applications of engineering project decomposition structures, spatial + classification coding, considering different needs such as project construction and operation management, engineering measurement, archives management, and big data analysis, a "five-segment" digital highway model classification coding framework based on the ISO 12006-2 is proposed. Subsequently, an automated coding approach based on parametric modeling and rule engines is introduced, significantly enhancing the efficiency and accuracy of coding work. The practical application of digital highway model identification coding in highway engineering information systems demonstrates its ability to establish effective connections between information models and smart construction management business data, thereby providing support for the sharing and transmission of data throughout the entire lifecycle of highway projects.