For the control allocation problem in the field of aeronautics and astronautics, a control allocation method based
on max direction derivative(MDD) fixed-point(FXP) iteration is proposed. MDD is defined as the unit vector which has the
max derivative among all the directions of the unit vector at current iteration point. Along the MDD direction, the increment
of next iteration point is estimated by using least square fitting of the increments of the former and current iteration point,
which is taken as a update for the increment of current iteration along the MDD direction. The convergence of the method
is also proved. Finally, the comparison of different methods is carried out. The simulation results show the effectiveness and
the rapidity of the proposed method.