Diversification is an important business strategy of a modern enterprise, which is a natural hand key choice during the growth process of the modern enterprise. It is unavoidable to encounter all sorts of risk in the process of operation for small and medium-sized enterprises in our country because of their limited objective conditions. It is an import thing to consider how to make the financial risk diversification controlled and evaded effectively. Based on accounting, management and other related theories, the paper makes a deep research on the risk factors generating in the diversified operating of small and medium-sized enterprises, and puts forward the way how to evaluate and control the risks.