Abstract: LS－SVM is computationally more efficient than the standard SVM,but unfortunately the sparseness of standard SVM is lost,another problem is that LS－SVM might lead to estimates which are less robust with respect to outliers on the data or when the assumption of a Gaussian distribution for the error variables is not realistic.In this paper,a new modified version,robust LS－SVM,which can obtain robust estimates by applying a weighted LS－SVM and achieve the sparseness by doing pruning based upon the support value spectrum,is adopted and introduced into the aerodynamic parameter fitting.The simulation results indicate that robust LS－SVM has a better fitting of aerodynamic parameter with features of simplicity,precision,robustness and rapidness to learn.It is a good method which is worthy of popularizing and promoting in calculating of aircraft’s flight trajectory．