An on-demand model selection method is proposed based on the guidance of on O-RGPS（Ontology annotated Domain Role/Goal/Process/Service Model Repository） domain modeling framework.It can realize the automatic modeling of expected goal requirements by using the ontology annotated semantic association between domain ontologies and domain models.It provides an automatic requirement modeling algorithm which utilizes grammatical element similarity calculation and goal similarity calculation to select the best suitable domain goal model.The effectiveness of this algorithm is demonstrated by a case-study in urban transportation system in the end.