The leaves of the Stevia rebaudiana Berton plant contain a variety of steviol glycosides used as natural high-intensity sweeteners. Rebaudioside D (RebD), a steviol glycoside, exhibits a sweetness profile similar to that of sugar but has very low aqueous solubility. In this study, we developed a method to dissolve RebD in a molten secondary component and prepared a solid-phase complex containing RebD. After screening, erythritol was selected as the optimal second component. For the erythritol/RebD complex, an aqueous solubility of 3000-4500 mg/L RebD was achieved, a 5- to 6-fold increase compared to saturation. The dissolution rate was also improved compared to RebD alone. Different cooling temperatures and rates were evaluated and found to affect the morphology and solubility of the complex. The solubility of RebD can be greatly improved by preparing binary complexes using the method proposed in this work.