With the advent of the Model Driven Development (MDD), models are replacing code as the major artifact in software development. These models are typically specified using OMG?s Unified Modeling Language (UML) . In MDD, model transformation and model composition are two essential model management tasks. Model transformation has been extensively researched while model composition still needs further investigation. The goal of this paper is to propose a guidance for model composition (specifically for class diagrams composition) based on match rules, model transformation rules and model composition strategy. Moreover, we present UML Profile for Model Composition and make an analysis about UML?s composition mechanism.