β-Ga2O3 is one of the most promising ultrawide band-gap semiconductor materials, but its crystal defects are not investigated comprehensively. The low angle grain boundaries of β-Ga2O3 crystal mainly exists in (100) plane. The existence of low angle boundary can destroy the integrity of the crystal structure and reduce the quality of crystal. The macroscopic analysis and microstructure characterization of the low angle grain boundaries in the β-Ga2O3 crystal grown by edge-defined film-fed growth method were carried out by chemical etching analysis and transmission electron microscopy. The results show that the shape and orientation of the etch pits on both sides of the low angle grain boundary are consistent, and the misorientation angle of the low angle grain boundary is 3°. In addition, the low angle grain boundary can cause the double peaks and broadening in the X-ray rocking curve. The gap in the study of low angle grain boundary is filled based on the characterization of the microstructure of low angle grain boundary in β-Ga2O3 crystals.