β-Ga₂O₃ is a novel wide bandgap semiconductor material with excellent performance, which has great potential applications in high power electronic devices and deep ultraviolet detectors. By doping with In³⁺ ions, the bandgap and optical properties of β-Ga₂O₃ can be adjusted, further expanding its application range. In this study, β-Ga₂O₃:9%In and β-Ga₂O₃:15%In single crystals are prepared using high-purity Ga₂O₃ and In₂O₃ as raw materials by the optical floating zone method. When the growth rate is 5 mm/h, the crystals exhibit a phenomenon of transparency loss. Observation under an optical microscope reveals the presence of numerous bubble defects in the crystals, which mainly appearing strip-like and spherical shape. Length of the strip-like bubbles ranges from 50 to 200 μm and extends along the [010] crystal direction. Observation under a scanning electron microscope reveals uniform elemental distribution around the bubbles, with no evidence of impurity element accumulation. These findings suggest that the formation of defects is related to the high-temperature decomposition of In₂O₃, where the generated gas is not timely discharged, entering the crystal interior with the crystallization of the melt to form bubbles. After optimizing the crystal growth process, the problem of opacity caused by bubble defects is effectively resolved, resulting in transparent β-Ga₂O₃:9%In single crystal with a full width at half maximum of the rocking curve as low as 44 arcsec and significantly improved crystalline quality. This study provides a solution for growing high-quality β-Ga₂O₃:In bulk single crystal, laying a foundation for a deeper understanding of its optoelectronic properties.