Abstract: The method of ridge estimation to treat equality constraint inversion(ECI) with ill-posed constraint matrix is put forward.The solution equation and evaluating precision by mean square error are deduced.For the case that the ridge parameter is difficult to determine in ridge estimation to treat ECI with ill-posed constraint matrix,the L-curve method,generalized cross-validation(GCV) and the ridge mark method are introduced and given.Through some cases of inversion,the comparisons are carried out among the L-curve method,GCV and the ridge mark method,and some conclusions are obtained.