In interferometric fiber-optic gyroscopes(FOGs), when the modulation signal exceeds the limit and undergoes a 2π reset, a 2π phase difference appears between the modulation amount of the modulation-signal input and the input angular velocity.This causes the interference phase to shift left or right by 2π, i.e., a cross-fringe operation. In a FOG closed-loop system, the error caused by the cross-fringe operation is reflected in the random-walk coefficient and nonlinearity. In this study, a cross-fringe error-cancellation mechanism is established by optimizing the modulation scheme, which can cause the cross-fringe errors to cancel each other, thus greatly improving the nonlinearity and random-walk coefficient. After simulated and physical verification, the results show the effectiveness of this method.