| Ground-Source Heat Pump that makes ground its heat source is energy-efficient and doesn't damage to environment, which meets the need of being developable continually. As green technique of energy-saving HVAC, it's widely applied in heating and cooling engineering projects in the world, especially in Europe and America.GSHP is divided into three types according to its heat source: soil heat pump, ground water heat pump, surface water heat pump. Soil heat pump becomes the core of research on GSHP ,because it can avoid water pollution and geologic destroy which are caused by water heat pump. Underground heat exchange is the key point of this technique. Simulation is an effective method to save time and costs. With the development of computer, complicated engineering problem could be solved by numerical calculation. Finite element is a popular method for CAE (computer Aided Engineering).To simulate underground heat exchange, overseas experts focus on building heat transfer model and solving it by computer program. Some researchers have developed software for different operating conditions. Researches in our country are limited in establishing model for a special experimental system to found fit the measuring results well. All the work are mostly about single heat source, however, the studies of multi-source heat pump are required to accommodate the large-scale application of GSHP and the growing value in using ground energy. The article proposed multi-hole technique concept, and simulated the process of its underground heat exchange for characteristics multi-analysis.Common heat exchanger models are based on the theories of line heat source and column heat source. This paper introduced some typical models in details and presented each graph. On condition that only the heat transmission in ground is taken into account, familiar concentric tube model and U-tube model could be predigested into cylindrical model which is much more practical than line source model. Therefore, cylindrical model was selected for our calculation.The multi-hole heat source transfer model was established on the basis of finite element numerical platform. We disposed 25 holes orderly and 40 holes crosswise in an area of 16*16 square meters and every borehole have same structure. Numerical grids were generated for the model by using an automated parametric grid generation algorithm. On the surface of each borehole where temperature changed fiercely, the element size was made 5cm instead boundary element 20cm in accordance with pre-calculation. In this way, calculation precision was improved, while the resource of computer was saved. Initial temperature distribution was defined by combining theoretical principle with experimental results. Regarding the power of equipment operating as invariable, we loaded the borehole surface elements with thermal-heat flux to work out solution. The node temperature dates at the end of heat exchange process were picked up for results treatment. Simulations of different working conditions provided the effects of various parameters on underground temperature field distribution. Such as initial temperature, operating strategies (continuously, intermittently), diameter of the borehole, heat loads, cycle period, backfills and so on.The influences of changing parameters on the process of heat exchange, the performance of system and the efficiency of ground energy using were discussed by analysis of the characteristics of underground temperature field distribution. 1．Transient temperature distribution around each borehole of the multi-hole system showed the same feature as single-hole system when they worked on certain conditions. System operating frequently caused interference of each other which is different from single-source, so the whole temperature field would be changed. The fall of whole temperature turned to be gently and steady as system operating for heat produced. 2．Initial ground temperature value influences heat process obviously. Simulating heating status, if we increased the init...
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