Fouling in geothermal systems reduces the efficient exploitation of geothermal fluids. In this paper, a scaled geothermal well in Bono, Hebei is selected. The type of scaling is analyzed while the scale inhibitor filling device is developed and designed and the scale inhibitor filling test is carried out in the field under various working conditions, with which the scale inhibition rate is calculated and evaluated. The results showed that the scale components of the geothermal well were aragonite and calcite, and that the scale inhibition rates of the four selected scale inhibitors were all above 80%, among which the best one scale inhibitor reached 94.49% at a spiking concentration of 35.95 mg/L. The scale inhibition effect in one heating season shows that the chemical scale inhibitor can effectively solve the calcium carbonate scaling in wellbore and surface equipment.