The characteristics and mechanism of the oxide layer in ELID groove profile grinding process were investigated. The non-uniform contact during ELID groove grinding and the effect of oxide layer on the grinding force and the surface roughness were studied. As the current increases from 1 A to 4 A, the thickness of oxide layer decreases from 35.33 μm to 11.07 μm. Meanwhile, the normal grinding force increases from 7.06 N to 36.12 N, and the tangential grinding force increases from 1.62 N to 4.47 N. R_av increases from 0.256 μm to 0.355 μm, and R_ap increases from 8 nm to 13 nm. The result indicates that as the thickness of oxide layer decreases, the grinding force and surface roughness increase, while as the thickness of oxide layer increases, the grinding force and surface roughness decrease.