The support of large aperture optical lens is one of the key technologies of the precision optical instrument. The support with multi flexural brackets is widely used in the support of the optical lens because it can eliminate the thermal aberration efficiently and make the lens act with uniform stress. A structure of a support of optical lens is designed with L-shape multi flexural brackets. A theoretical derivation of its mechanic index is also presented. Take a typical lens as an example, the relationship of the number of brackets and the lens aberration is also given. The results indicate that we can set the distance between the center of the lens and the support point closer and the length of the brackets shorter to to make the aberration of the lens better. At last, the relationship and the geometric indexes of the support is obtained. The results of this article can be the references for the applications of the support with multi brackets.