A nonuniform distribution of axial velocity along the spanwise direction on the impeller outlet is presented,based on which an approach is proposed to design the twisted blade for micro axial fans considering the nonuniform axial velocity.By computational fluid dynamics(CFD) technique,the aerodynamic performances of different types of twisted blades are numerically investigated in the design and on the off-design operating conditions.The aerodynamic performances of the enlarged model fans in self-stimulated domain are compared with that of the micro-scale fans in non-self-stimulated domain.Results indicate: in non-selfstimulated domain,the pressure is almost linearly increased with the decreasing flowrate,there are no maximum pressure and no stalling point,and the efficiency curve tends to much smoother.Compred with the free vortex twisted blade,the twisted blade designed by rigid vortex generates higher pressure,but has lower efficiency.The improved ratio of hub to shroud may raise the pressure and efficiency for the micro axial fan.