Abstract: In order to obtain the suitable micro fan which satisfied the design requirement, based on Response surface optimization, using CFX software, the flow pulsation characteristics inside the micro diagonal fan with split joint structure are designed and the flow characteristic is researched by using SST k-ω equation. The results shown that, at the designed flow rate, the static pressure at the outlet of the diagonal fan is 9% higher than that of the original axial fan, and the axial thickness of the impeller is shortened by 30%, and the static pressure curve at the outlet of the fan is smooth and the variable flow performance is robustness. The high efficiency region is near the designed flow rate. Because of the split joint structure of diagonal and meridian accelerated diagonal, the static pressure distribution on the blade surface has obvious front and rear fields.