The aim of this paper is to suggest one efficient method for the various requirements of performance during the process designing and producing an impeller. The study considers that the revisions of a pitch angle of an impeller at an axial turbo fan affect an air flow rates and a static pressure rise. The axial turbo fan specified with the 250 Pa maximum static pressure and 1300 CMH fan air flow rates was tested and analyzed by CFD. The Numerical results show that the air flow rates are calculated to 1,175 CMH, 1,223 CMH, 1,270 CMH, 1,340 CMH and 800 CMH in cases that the pitch angles are $44^{circ},;49^{circ},;54^{circ},;59^{circ},;and;64^{circ}$ respectively. Also the static pressure rises are shown to 108 Pa, 122Pa, 141 Pa, 188 Pa and 63 Pa at the same cases. The air flow rate is increased linearly according to the changes of the pitch angle from $44^{circ};to;59^{circ}$ and the maximum air flow rate passing the impeller is increased to $13\%$ over at the case of $59^{circ}$ pitch angle compared with the reference case of $54^{circ}$ pitch angle. The static pressure rise is increased linearly according to the changes of the pitch angle from $44^{circ};to;54^{circ}$, too. The static pressure rise at the $59^{circ}$ pitch angle is increased to $33\%$ over compared with the $54^{circ}$ pitch angle. The result shows that the revisions of pitch angle make the static pressure rise increase widely. However the air flow rates and the static pressure rise at the $64^{circ}$ pitch angle are suddenly decreased because of over-changed pitch angle.