Understanding the pathogenic crystallization of calcium oxalate (CaOx), a major constituent of kidney stones, is crucial in developing effective treatment strategies. In this work, the interactions between lysozyme and CaOx during crystallization have been investigated. Further investigations into the crystal morphology, size, quantity, and nucleation time of the lysozyme have been designed. The results reveal that CaCl2 could act as an effective precipitant for lysozyme crystallization. The formation process and structure of the distinctive composite CaOx-lysozyme crystal has been investigated. The addition of lysozyme promoted the formation of individual CaOx crystals by preventing the crystal aggregation in the solution. The presence of lysozyme induced a transformation in the CaOx crystals from calcium oxalate monohydrate to calcium oxalate dihydrate. These findings contribute to a better understanding of protein-CaOx interactions and their implications in kidney stone pathogenesis.