As a primary component of the horizontal ground heat source pump (GSHP) system, spiral coil-type horizontal ground heat exchangers (HGHEs) have been widely used because of their superior heat transfer performance. To evaluate the ground temperature rise, many analytical solutions for spiral coil-type horizontal ground heat exchangers have been proposed. This study suggests a load sharing ratio, which is essential to consider the presence of an outlet pipe in the analytical solution to achieve more accurate prediction of ground temperature rise. This ratio enables the determination of the spiral coil heat exchange rate. Thus, a three-dimensional numerical model of the spiral coil-type ground heat exchanger was developed. Then, the effects of the factors influencing the load sharing ratio were investigated through a parametric study. Finally, the linear regression method was used to develop a load sharing ratio model. The load sharing ratio model may provide a more accurate prediction of ground temperature rise and help us design spiral coil-type HGHEs reliably.