In the current big data background, data mining and decision making algorithms are widely used in financial management. In this paper, the author analyse enterprise financial management and decision making based on decision tree algorithm. The enterprise can establish the financial management model by the result of data mining, and then establish a whole set of financial decision system. The empirical analysis shows that the decision model proposed in this paper can well analyse the financial status of enterprises, and can realize the functions of enterprise financial analysis and decision-making management. In the enterprise financial diagnosis decision stage, the enterprise managers should not only pay attention to the financial management status reflected by the financial statements, but also need to comprehensively consider the environment of the receiving enterprise, as well as the changes in the specific operating conditions.