Mini wind generator is an efficient way to save electricity and develop the potential green wind energy in city environment. The material and structure design of the supporting frame is a key factor to ensure the generator work fluently and safely for manufacturing engineering. In this research, the dynamic properties of the frame with different structure materials are analyzed by finite element method. The epoxy frame has the fewest number natural frequencies coinciding with the generator working revolution frequency. And the mode shapes of epoxy frame of different orders are achieved by FEM. A new kind of analytical method, key node component-displacement criterion is proposed with respect to the displacement characteristic of the frame under different mode orders. This criterion provides a new approach in evaluating the deformation characteristic of the dynamic properties of mechanical structures.