The study explores the enhanced genome-editing activity of iGeoCas9, an evolved version of *Geobacillus stearothermophilus* Cas9 (GeoCas9), by focusing on the WED domain mutations. These mutations improve DNA unwinding speed, leading to more efficient R-loop formation and reduced PAM specificity. The WED domain mutations enable iGeoCas9 to function effectively in magnesium-restricted conditions, which are typical in mammalian cells. Biochemical and structural analyses reveal that the WED domain mutations enhance interactions with the target DNA, accelerating DNA unwinding and improving genome-editing efficiency. The findings suggest that rational engineering of the WED domain can boost the activity of other CRISPR-Cas9 enzymes, providing a general strategy for enhancing genome-editing tools.The study explores the enhanced genome-editing activity of iGeoCas9, an evolved version of *Geobacillus stearothermophilus* Cas9 (GeoCas9), by focusing on the WED domain mutations. These mutations improve DNA unwinding speed, leading to more efficient R-loop formation and reduced PAM specificity. The WED domain mutations enable iGeoCas9 to function effectively in magnesium-restricted conditions, which are typical in mammalian cells. Biochemical and structural analyses reveal that the WED domain mutations enhance interactions with the target DNA, accelerating DNA unwinding and improving genome-editing efficiency. The findings suggest that rational engineering of the WED domain can boost the activity of other CRISPR-Cas9 enzymes, providing a general strategy for enhancing genome-editing tools.