In this paper, a superposition distortion index K_A2 is introduced to indicate the relationship between the distortion intensity and the fan speed. The data to calculate the K_A2 was obtained by the distortion experiments using the two stages axial flow fan and distortion screens. A number of conventional distortion indecies such as K_ra2, DI, D_min, K_θ, K_D2, DC60 are presented to evaluate the each radial and circumferential distortion intensity. In previous paper, both radial and circumferential distortion indecies are expressed in one figure to evaluate the distortion intensity more accurately. This method, however, cannot tell the influence of the fan speed. The index K_A2 includes the radial distortion index Kra2 and the circumferential distortion index K_θ, the influence of fan speed. The influence of fan speed was obtained from the stall margine decrease of the fan characteristics curves.