Abstract: This study investigated the preparation of microcapsules comprising polymerized whey protein and quercetin as the sole wall and core materials, respectively, and produced quercetin microcapsules with high encapsulation efficiency, quality, and stability. The microcapsules were prepared using the orifice-coagulation bath method, and the encapsulation efficiency was adopted as the assessment indicator in determining the optimal process conditions via single-factor experiments and an L₉(3⁴) orthogonal array experimental design. The properties of the microcapsules prepared under the optimal process conditions were analyzed using scanning electron microscopy, particle size and Zeta potential measurements, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, Raman spectroscopy, and an in vitro digestion study. The optimal process parameters for microcapsule preparation were as follows: core:wall ratio: 1:7; quercetin concentration: 1 mg/mL; CaCl₂ solution concentration: 1.6%; stirring time: 50 min. The microcapsules prepared under these conditions exhibited an encapsulation efficiency of 96.72% and a uniform particle size distribution. The spectroscopic measurements and results of the in vitro digestion study indicated that the prepared microcapsules also displayed high levels of formability and stability and the wall material had good possessed sustained-release properties. This study can serve as a theoretical basis for the optimization of microcapsule preparation and the practical application of microcapsules in the food industry.