To streamline and strengthen the process of acquisition, representation and exploitation of scenarii of railroad accidents, it is necessary to harmonize and standardize the terminology used by domain experts. The research aims to significantly improve analytical activities and operations of the various safety studies, by tracking the error in system, hardware, software and human. This paper presents the contribution of ontology to modeling scenarii for railroad accidents through a knowledge model based on a generic ontology and domain ontology. After a detailed presentation of the state of the art material, this article presents the first results of the model developed.