The invention discloses a multi-scale porous structure light weight modeling method oriented to 3D printing, and belongs to the field of computer aided design and industrial design manufacture. Undera condition that characteristic constraints and a stress condition are given, through a compact support radial basis function interpolation, a smooth multi-scale porous model is constructed; the multi-scale porous model is applied to light weight modeling, and a feasible solving solution is given; through the 3D printing, an entity experiment model is obtained and is subjected to engineering stress verification; according to engineering verification result analysis, a parameter is corrected to enable the hole change of an optimization model to more approach to practical stress requirements; and through the above loop iteration process, a light weight model which meets stress requirements is obtained. By use of the method, a light weight purpose of the entity model can be truly realized, sothat the light weight design optimization period of the model is greatly shortened, the porous structure obtained by design has the advantages of smoothness, full connectivity, controllability and quasi-self-supporting, and the effectiveness and the manufacturability of light weight can be accurately guaranteed.