Numerical aerodynamic optimization is an automatic design method via computational fluid dynamics, optimization theory and fan characteristic. It can implement multi-objective optimization and multi-parameter combinatorial optimization with less dependency on designer爷s experience. Fan design using numerical aerodynamic optimization focus on four key technologies: Fan blade passage flow field numerical method; Numerical optimization method with a good search capability; Parameterization description method of three-dimensional blade shape using Computer Aided Geometric Design Technology; The construction methodology of multi-objective function for aerodynamic performance. Software with friendly user interface is built by above four modules. 3D blade optimization examples verify that the design of the blade using this software are reliable and high-efficiency, it can shorten design period.