Abstract: The concept of elastic support is defined in thispaper, for the real contacts and constraints between structural bars, basedon the concept of conventional support in structural mechanics. Two basic systems ofelastic supports are established, with two feedback basic equations,and the basic formulas of the rod end constraint stiffness in bothdirections are obtained. The elastic support analysis method of structure mechanics isthen formulated. The finite element equations for the elasticsupport analysis method are obtained. With the elastic support method, onestep moment distribution method can be derived, which would improve the separated floor method and the D value method a greatdeal.