Abstract: Facing the needs of digital twins for the whole life cycle of railway, aiming at the problems of independent expression, decentralized management and difficult in-depth integration of continuously changing railway geographic and geological data for a long time, this paper proposes an integrated expression model of the three-domain association of "ontology domain-change domain-state domain" for railway geographic and geological data, which takes railway geological and geological elements as an inseparable whole. This paper defines a multi-level spatial -temporal change association relationship between state level-entity level-process level, with spatial-temporal change as the center and change participants (elements), drivers (events) and presentation modes (processes), constructs a knowledge graph of railway geological data with multi-domain association, and finely portrays the semantic association relationship between geological elements-events-processes. The importance and potential of the model in typical tunnel construction applications are analyzed.