Abstract: Ultra-thin grain-oriented silicon steel, a key material for ultra-high voltage power transmission equipment over ultra-long distances, must combine high magnetic induction with low iron loss. However, there is a trade-off between magnetic induction and iron loss. Achieving an optimal synergy between these two properties remains a pivotal technical challenge in this field. To address this challenge, the effects of cold rolling reduction on the microstructure, texture evolution, and magnetic properties of ultra-thin grain-oriented silicon steel were systematically investigated using electron backscatter diffraction （EBSD） and X-ray diffraction （XRD）. The underlying mechanisms were elucidated, which led to the identification of the optimal cold rolling reduction. Consequently, ultra-thin grain-oriented silicon steel exhibiting both high magnetic induction and low iron loss were successfully fabricated. The results indicate that as the cold rolling reduction increases, the number of shear bands in the cold-rolled sheet increase, the intensity of the 111〈112〉 cold-rolled texture strengthens, and the annealed sheet exhibits a refined average grain size. When the cold rolling reduction increases from 62.9% to 74.1%, the number of Goss nuclei increases, which exhibits significant advantages in both orientation and size. However, when the cold rolling reduction reaches 81.4%, the nucleation of 210〈001〉 and 113〈361〉 orientations within the shear bands becomes dominant, thereby weakening the growth advantage of Goss grains. As a result, the magnetic induction shows an initial increase followed by a decrease with further increase in cold rolling reduction. The highest magnetic induction is obtained at cold rolling reduction of 74.1%, where the η-fiber accounts for the highest proportion. As the cold rolling reduction increases from 62.9% to 70.3%, the grain size decreases substantially, leading to an increase in hysteresis loss and consequently an overall rise in iron loss. When the reduction further increases from 70.3% to 81.4%, the rate of grain refinement is slowed, resulting in a limited increase in hysteresis loss, while the thinning of the sheet leads to a significant decrease in hysteresis loss, thereby causing the iron loss to first increase and then decrease. The optimal magnetic properties are achieved at a cold rolling reduction of 74.1%, with magnetic induction of 1.90 T and iron loss of 12.91 W/kg.