In recent years, ground source heat pump systems are recognized as effective renewable energy heating, ventilation and air-conditioning systems. In ground source heat pump systems, ground heat exchangers serve as heat-conducting medium with vertical distribution or horizontal distribution. Many remarkable studies were carried out in the past few years. However, most of the existing reviews mainly contributed to vertical ground heat exchangers research along with design, performance, and applications. A systematic summary on analyzing thermodynamic performance of horizontal ground heat exchangers in ground source heat pump systems is essential. Therefore, this review aims to summary the optimal thermodynamics analysis on horizontal ground heat exchangers in ground source heat pump systems. According to the analytical solutions, numerical simulations and experimental measurements, the reviewed research articles are classified into four sub-categories: linear-loops, slinky-coils, helical-coils and others. The optimal thermodynamic performance for each study is illustrated and discussed. Furthermore, assessments and comparisons among different horizontal ground heat exchangers are summarized. In the end, future development suggestions and research direction recommendations related to ground source heat pump systems with horizontal heat exchangers are given.