In this paper, we present a multi-formalism modeling framework (abbreviated by MFMF) for modeling and simulation. The proposed framework is defined based on the concepts of meta-models and uses object-orientation to overcome the complexities and to enhance the extensibility. The framework can be used as a basis for modeling by various formalisms and to support model composition in a unified manner. The structure of the framework is organized in four layers: (1) the metaformalism layer, (2) the formalism layer, (3) the class-model layer, and (4) the model layer. The basic concepts of the framework are formally defined using object constraint language (OCL) and have been illustrated using some examples. We have also explained the model composition structure and the solution strategies of the proposed framework. A prototype tool for the proposed framework is implemented, which is briefly introduced in this paper.