Thermo-physical properties of the ground play a vital role in heat transfer of ground heat exchangers (GHE) of ground source heat pump (GSHP) systems. Design and planning of GSHPs need to determine ground thermo-physical parameters by ground investigations. This paper deals with reviewing of ground investigations of GSHP systems from three aspects. Survey to geological setting is first introduced with taking into account thermo-physical properties of geological materials and different types of GSHPs. Then, determination of thermal properties of the ground is discussed for both laboratory and field tests (e.g. Thermal Response Test (TRT)). The limitations and advantages of the existing methods are compared and analyzed. Furthermore, in order to clarify groundwater advection effects on thermal performance of GHE, investigations to hydraulic conditions are reviewed. Finally, strategies of organizing ground investigations for different types of GSHPs are discussed. This work provides useful information to optimal sizing and installation of GSHP systems. (C) 2016 Elsevier B.V. All rights reserved.