Abstract: Relying on the existing engineering experience data or the short-term heat transfer test results of middle and deep borehole heat exchanger, an extensive method is typically used to design the middle and deep borehole geothermal heat pump heating system. It leads to the unreasonable configuration of the borehole heat exchange system and the reduction of the reliability and economy of heat pump heating system. In order to improve the design status of the middle and deep borehole heat exchange system, a dynamic simulation method is adopted in this paper, considering the design load, cumulative load and hourly load distribution law, to analyze the unsteady characteristics of deep-buried geothermal resources in the long-term dimension and the temperature-self-recovery performance of rock and soil, and determine the designed water supply and return temperature at the source side based on the "annual periodic cooling and heat balance of final state" of underground rock and soil. And optimization method of source-side design flowrate based on the optimization of the average annual life-cycle cost on the ground source side is proposed. Taking an engineering project as an example, the optimization design of source-side parameter is given.