Based on the modified least median of squares （LMedS）regression

a robust approach of motion estimation from the space position vectors of 3-D feature points is put forward.First initial estimation is obtained by the primary LMedS

then we re-estimate motion parameters with an iterated reweighted estimator

in which a hybrid weight function of Huber weight and Tukey weight takes place of the dichotomy weight in the primary LMedS.This algorithm alleviates the difficulty of deleting some outliers while SNR is too low

so can get better accuracy of estimation. Computer simulations show that its performance is satisfactory.