The article examines economic and mathematical modeling of the process of managing the investment projection for the business entity. The aim is to analyze investment management in order to design and apply economic and mathematical methods that would optimize the process. The article defines the investment planning process, highlights the main stages and steps in the process of investment planning, shows the process of optimizing the management of investment design using economic and mathematical modeling. It is suggested to use methods of network planning and management for the development of economic and mathematical models of the investment management process design. We propose a network model that is appropriate for the process that allows a business entity to efficiently organize its investment planning processes. The paper presents an actual example of using the proposed network model for developing an investment project for the opening a company for the construction phase and finishing the production premises. For this example, the analysis has been carried out, along with the ordering and coding of existing works, an appropriate roadmap has been built, network modeling parameters have been calculated and a calendar schedule has been constructed for the process of investment planning. The findings and conclusions of the article suggest that the proposed network modeling could be used as a tool for solving problems of controlling the investment planning process during the activity of an economic entity and as such contributes to its efficiency and leads to increased competitiveness. The results can be used by any business entity engaged in investment activities in the current economic conditions and seeking to optimize their time and cost expenditure.