The diversification pattern formed after mergers and acquisitions of enterprises belonging to different industries often leads to a sharp rise in management costs because of the low degree of resource correlation between enterprises. Resource relevance refers to the relevance, transferability and transfer efficiency between the existing resources of the enterprise and the resources owned or needed by the merged enterprise. Diversified operations with low correlation can't enjoy resources, which leads to low resource occupation efficiency, and management span and management failure lead to increased management costs, which further affects the failure of diversified operations after mergers and acquisitions. In addition, due to the highly dispersed business fields and different management modes in different fields, higher requirements are put forward for managers of enterprises, and the contradiction between centralization and decentralization within enterprises is also aggravated. If we don't grasp it well, it will easily lead to financial crisis. Mixed mergers and acquisitions involve industries that they are completely unfamiliar with. They basically have no experience, no talents, no social relations and only a certain amount of funds. However, if they put their money into an unknown black hole and underestimate the changes in the market, they still stay in the simple replication of successful experiences. The most direct consequence is a financial crisis.