As an inevitable trend of the development of the times, this paper explores the application of big data technology in enterprise financial decision-making and constructs a complete process of enterprise financial management based on data mining. The improved k-Means algorithm is used to complete the clustering analysis of financial data, and the CAP algorithm is applied to the identification and classification of financial problems to realize the early warning of the financial crisis. Combining analysis and early warning, the financial decision management system in enterprise cloud accounting is constructed using the ID3 algorithm. Company H, a real estate enterprise, was selected as a research case and analyzed by collecting financial data and using data mining methods. The profitability, solvency, operations, growth, and cash capacity scores for Company H in 2021 are 11.19, 4.24, 4.94, −0.56, and −0.48, respectively. The changes in Company H’s profitability, solvency, and operations are relatively stable from 2013-2019.