Abstract: In the future, the distribution network will become a comprehensive service platform for energy, electric power, and information services. In order to lead or adapt to the new trend, domestic power companies are gradually shifting their investment and construction focus to the distribution networks. With the delineation of the " Carbon neutral" policy and the reform of transmission and distribution prices, the internal and external environments of the distribution network investment have undergone profound changes, making the distribution network faced with challenges from many aspects. This article discusses the cost-effective investment theory and its key technologies around how to improve the efficiency and benefits of the distribution network investment. First, it distinguishes the distribution network investment and planning based on the optimization factors and optimization goals. Then it summarizes the related researches in the field of investment optimization. Subsequently, the business processes and characteristics of the ideal distribution network cost-effective investment business are explored, and the complexity of the current distribution network investment and the practical focuses of cost-effective investment are analyzed and summarized. On this basis, a method for the implementation of cost-effective investment in the distribution network is proposed, and its technical structure, implementation structure, and technical characteristics are analyzed and explained by listing the application features and functions embedded in the cost-effective investment platform. Finally, it illustrates the characteristics and research status of the key technical issues in the cost-effective investment of the distribution networks, such as the complex feature extraction technology, the risk management and control, and the time sequence deduction technology, in order to provide some thinking and reference for distribution network investment decision-making under the new situation.