Pile geothermal heat exchanger is characterized by bigger pile diameter and shallow buried depth，and current studies presented the analytical solution models only considering soil conduction ignoring the thermal property difference between grout and soil which would induce the calculation error for big pile diameter. A conduction numerical solution model considering the thermal property difference was developed to analyze the heat transfer influence of pile geothermal heat exchanger induced by thermal parameter difference. Results showed that conductivity difference had little impact on the heat transfer when the operation time was long and the difference of specific heat would induce big error of the ground heat exchanger design capacity and the bigger the pile diameter was，the more obvious the calculation error.