The aim of this paper is to propose a service oriented decision support system based on an ontology-driven uncertainty model (OntoBayes). OntoBayes consists of knowledge and decision model parts. The former is the integration of ontologies and Bayesian Networks while the latter can describe different decision models. OntoBayes gives a solution to deal with uncertainty and structure complexity and provides decision models by decision making. In order to construct a decision support system, a service oriented framework and architecture will be introduced finally.