In the context of China’s electric power reform, issued in May 2019, the “Transmission and Distribution Pricing Supervision Measures” have changed asset accounting in grid enterprises and therefore affected cost accounting in grid projects. This paper proposes a dynamic cost calculation model based on system dynamics and takes a power grid company as an example. On this basis, a sensitivity analysis of power grid engineering was conducted to determine the impacts of key factors of power reform on life cycle cost (LCC). Finally, suggestions for cost accounting and cost management were proposed.